If you have a Fun Fly Stick, then pull it out and watch the video below. If not, don't worry - you can do most of these experiments with a charged balloon (one that you've rubbed on your hair). Let' play with a more static electricity experiments, including making things move, roll, spin, chime, light up, wiggle and more using  static electricity! [am4show have='p8;p9;p97;p58;' guest_error='Guest error message' user_error='User error message' ] Materials:
  • sheet of paper
  • two empty, clean soup cans
  • aluminum foil
  • long straight pin
  • three film canisters (or M&M containers or small plastic bottles)
  • penny
  • neon bulb (optional)
  • small styrofoam ball or single packing peanut
  • fishing line or thread
  • chopstick
  • foam cup
  • small aluminum pie tins or make your own from aluminum foil
  • hot glue with glue sticks
  • Fun Fly Stick (also called "Wonder Fly Stick")
This video show you how to get the most out of your Fun Fly Stick. If you don't have a Fly Stick, simply use an inflated balloon that you've rubbed on your head. In the video, the Electrostatic Lab is mounted on a foam meat tray I found at the grocery store.
  Download Student Worksheet & Exercises The triboelectric series is a list that ranks different materials according to how they lose or gain electrons. Near the top of the list are materials that take on a positive charge, such as air, human skin, glass, rabbit fur, human hair, wool, silk, and aluminum. Near the bottom of the list are materials that take on a negative charge, such as amber, rubber balloons, copper, brass, gold, cellophane tape, Teflon, and silicone rubber. When you turn on your Fun Fly Stick (or rub your head with a balloon), one end of the Fun Fly Stick takes on a positive charge and the other end holds the negative charge. When you rub your head with a balloon, the hair takes on a positive charge and the balloon takes on a negative charge. When you scuff along the carpet, you build up a static charge (of electrons). Your socks insulate you from the ground, and the electrons can’t cross your sock-barrier and zip back into the ground. When you touch someone (or something grounded, like a metal faucet), the electrons jump from you and complete the circuit, sending the electrons from you to them (or it). Exercises
  1. What is common throughout all these experiments that make them work?
  2. What makes the neon bulb light up? What else would work besides a neon bulb?
  3. Does it matter how far apart the soup cans are?
  4. Why does the foil ball go back and forth between the two cans?
  5.  Why do the pans take on the same charge as the Fly Stick?
  6.  When sticking a sheet of paper to the wall, does it matter how long you charge the paper for?
  7.  Draw a diagram to explain how the electrostatic motor works. Label each part and show where the charges are and how they make the rotor turn.
[/am4show]  

 

Now you understand how scuffing along a carpet in socks builds up electrons on the body, and how this negative electric charge affects other things (like your cat) when you reach a finger out to touch them. You also know how opposite charges attract and like charges repel, and the difference between balanced charges and unbalanced charges.


We’re going to dive into studying force fields. You may wonder what force fields have to do with a serious examination of physics like the one in this lesson. You probably consider force fields to be something you might hear about in a science fiction scene such as…


[am4show have=’p9;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]


Meanwhile, in section 27B of the Horse Crab Galaxy, First Mate Fred frets, “Captain Clyde! the force field is too strong. Our ship will never make it through.” “Never worry First Mate Fred!” exclaims Captain Clyde calmly. “I’ve increased power to the neutron-frapters so we will be just fine.” “Captain Clyde, that’s genius. You’re my hero!” First Mate Fred fawns.  


Truthfully, however, force fields aren’t just something for science fiction writers. They are actually a very real and very mysterious part of the world in which you live. So, what is a force field? Well, I can’t tell you. To be honest, nobody can.


There’s quite a bit that is still unknown about how they work. A force field is a strange area that surrounds an object. That field can push or pull other objects that wander into its area. Force fields can be extremely tiny or larger than our solar system. There are gravitational fields, magnetic fields, electric fields, and electromagnetic fields.



Click here to go to next lesson on Maxwell’s Third Equation.

[/am4show]


Overall, Maxwell’s four equations describe the fundamentals of electricity and magnetism. However, one look at these mathematical equations can make a high school student run screaming from the room, so we’re not going to dive into the sophisticated mathematics of the equations themselves, but rather what they really tell us about the relationships between the electric and magnetic fields.


[am4show have=’p9;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]



 
Gravitational forces, magnetic forces, and electric forces are all action-at-a-distance forces (sometimes called field forces), meaning objects can interact even they are not touching each other.  The Earth and a ball are attracted to each other, even when the ball is tossed high up in the air. Two magnets can push against each other even when they are not touching. Same thing with two electrons: the negative charge on the electrons create a repulsive force that pushes on each electron.


A way to picture a force field is to imagine an invisible bubble that surrounds a gizmo. If some other object enters that bubble, that object will be pushed or pulled by an invisible force that is caused by the gizmo. That’s pretty bizarre to think about isn’t it?


Well,  not really. If you’ve ever been around a baby, you know that you can detect a diaper change without even peeking in there. The baby created a stinky field. It’s an invisible area that you can detect around the baby which increases in stinky-ness the closer to the baby you get. On the other hand, if you can imagine someone making your favorite meal and you walk into the house after a hard day, you enter into a wonderfully aromatic house filled with your favorite smells, you’re entering another field that you can detect, and the closer you get to the stove, the more intense the field becomes.


Click here to go to next lesson on Electric Field Lines.

[/am4show]


A field changes the nature of the space surround the thing producing the field. A magnet produces a magnetic field which changes the nature of the space around it so that other magnets and magnetic objects are now influenced by it. Some magnetic fields (and other fields) are stronger than others, and now we’re going to learn how to measure the field strength of electric fields.


The electric field is a vector (it has magnitude and direction), and this is how you do it:


[am4show have=’p9;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]



 


Click here to go to next lesson on Electric Fields.

[/am4show]


Michael Faraday was the first to come up with the idea about electric fields. He thought of the space around a charged object as being filled with lines of force. He was trying to figure out a pattern that represented what the electric field looked like by imagining the electric field as a bubble around a charged object and how it would interact with another object that enters into that bubble. This is a little different than imagining a charge interacting with a charge. There’s a field interaction between the two charges. Every charge creates a bubble around it that in turn, affects the space within that bubble.


[am4show have=’p9;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]



 


Click here to go to next lesson on Using Spices to Detect Field Lines.

[/am4show]


Have you wrapped your mind around static electricity yet? You should understand by now how scuffing along a carpet in socks builds up electrons, which eventually jump off in a flurry known as a spark. And you also probably know a bit about magnets and how magnets have north and south poles AND a magnetic field (more on this later). Did you also know that electrical charges have an electrical field, just like magnets do?


It’s easy to visualize a magnetic field, because you’ve seen the iron filings line up from pole to pole. But did you know that you can do a similar experiment with electric fields?


Here’s what you need:


  • dried dill (spice)
  • vegetable or mineral oil
  • 2 alligator wires
  • static electricity source (watch video first!)

[am4show have=’p8;p9;p20;p47;p76;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]



Download Student Worksheet & Exercises


Here’s what you do:


1. Fill a saucer with vegetable or mineral oil.
2. Sprinkle small seeds or spices on top, such as caraway, anise, or dill (this one works best).
3. Build up an electric charge by either rubbing a balloon on your head, rubbing a PVC pipe with a wool sweater or mittens, or your favorite way to build up to a spark.
4. Bring the charged object near the oil – what happened to the spices?
5. Does it matter which end of the balloon/pipe/etc you hold near the oil? What if you move it a bit near the dish?
6. Stir the dill into the oil. Bring a charged object near and watch the dill spring up to touch the rod.


Troubleshooting:
If your dill isn’t moving at all, your object may be too ‘dirty’ (e.g. have too much oil from your fingers) on it to hold a charge. Clean it with rubbing alcohol after you use soap and water, and you should see better results.


What’s going on?
The dill/caraway/anise are all shaped like rods, which move to line up in the field (which is why round particles like cinnamon and pepper don’t work as well). The dill has a balance of charges – both plus and minus – and when you bring a charged object close, the negative charges in the dill are attracted to the balloon but the positive charges are repelled, so one side of the dill becomes minus and the other plus. Since the dill is free to move in the liquid, it lines up in the electric field to indicate the charge direction.


If you move the balloon just right, the attractive electrical charge will pull the lightweight dill right up out of the oil and onto the balloon. Have fun!


Exercises


  1. What happened when you brought a charged balloon near the dill?
  2. What side of the dill was attracted to the balloon?
  3. What happened when you brought two negative charges near the dill?
  4. Were you able to make the dill come out of the liquid and onto the balloon without touching the oil?

[/am4show]


Click here to go to next lesson on Weird Shapes and Field Lines.

It’s easy to see how the field lines go from a point charge, but what about around an oddly shaped object (like most objects are)? Here’s how you draw them:


[am4show have=’p9;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]



 


Click here to go to next lesson on Faraday’s Cage.

[/am4show]


British physicist Michael Faraday, famous for his many contributions to science including electrochemistry and electromagnetism.
British physicist Michael Faraday, famous for his many contributions to science including electrochemistry and electromagnetism.

Michael Faraday also discovered how you can have an electric field inside a charged conductor. Image you have a room within a room, and the inner room is made completely of metal. You can sit in the inner room with a static charge detector (like an electroscope), and when you charge the surfaces of both rooms, you’ll see sparks flying between the two rooms, but it’s peacefully (electrically speaking) quiet in the inner room. No charge is detected inside the inner room with your electroscope. You can have a bolt of lightning strike the inner room, but it still doesn’t register a charge inside the inner room. Why is that?


The inner room I’ve just described is called a “Faraday Cage”, and it’s often seen at science and magic shows because it absolutely defies common sense, until you really think about it. The inner room is shielding you from electric fields. Any closed conducting surface can be a Faraday cage. By closed, I mean electrically speaking. The cage can be a cage made of bars or chicken wire, but it’s still got to be electrically closed.  During the experiment, you can even run your hands on the inside of the room and still not get a shock from the sparks flying around between the rooms!


[am4show have=’p9;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]



The Faraday cage takes the electrostatic charges and redistributes them evenly around the exterior of the cage. As the cage distributes the charges, it cancels out the electric charges within the interior, making the cage a hollow conductor that has charge only on the external surface.


Click here to go to next lesson on Potential Energy.

[/am4show]


You’re already familiar with two different kinds of potential energy: elastic (like the energy stored in a rubber band) and gravitational (the energy stored in height). Now let’s take a look at electrical potential energy stored in an electric field:


[am4show have=’p9;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]



 


Click here to go to next lesson on Electric Potential.

[/am4show]


Ever wonder where the “volt” comes from? We’re going to look at this more in the next section on DC current, but here’s a snapshot overview of electric potential:


[am4show have=’p9;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]



 


Click here to go to next lesson on Static Electricity Fun.

[/am4show]


If you have a Fun Fly Stick, then pull it out and watch the video below. If not, don’t worry – you can do most of these experiments with a charged balloon (one that you’ve rubbed on your hair). Let’ play with a more static electricity experiments, including making things move, roll, spin, chime, light up, wiggle and more using  static electricity!


[am4show have=’p8;p9;p97;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]
Materials:


  • sheet of paper
  • two empty, clean soup cans
  • aluminum foil
  • long straight pin
  • three film canisters (or M&M containers)
  • penny
  • sheet of paper
  • neon bulb
  • small styrofoam ball
  • fishing line or thread
  • chopstick
  • foam cup
  • dozen small aluminum pie tins
  • hot glue with glue sticks
  • Fun Fly Stick (also called “Wonder Fly Stick”)

This video show you how to get the most out of your Fun Fly Stick. If you don’t have a Fly Stick, simply use an inflated balloon that you’ve rubbed on your head. In the video, the Electrostatic Lab is mounted on a foam meat tray I found at the grocery store.



Download Student Worksheet & Exercises


The triboelectric series is a list that ranks different materials according to how they lose or gain electrons. Near the top of the list are materials that take on a positive charge, such as air, human skin, glass, rabbit fur, human hair, wool, silk, and aluminum. Near the bottom of the list are materials that take on a negative charge, such as amber, rubber balloons, copper, brass, gold, cellophane tape, Teflon, and silicone rubber.


When you turn on your Fun Fly Stick (or rub your head with a balloon), one end of the Fun Fly Stick takes on a positive charge and the other end holds the negative charge. When you rub your head with a balloon, the hair takes on a positive charge and the balloon takes on a negative charge.


When you scuff along the carpet, you build up a static charge (of electrons). Your socks insulate you from the ground, and the electrons can’t cross your sock-barrier and zip back into the ground. When you touch someone (or something grounded, like a metal faucet), the electrons jump from you and complete the circuit, sending the electrons from you to them (or it).


Exercises


  1. What is common throughout all these experiments that make them work?
  2. What makes the neon bulb light up? What else would work besides a neon bulb?
  3. Does it matter how far apart the soup cans are?
  4. Why does the foil ball go back and forth between the two cans?
  5.  Why do the pans take on the same charge as the Fly Stick?
  6.  When sticking a sheet of paper to the wall, does it matter how long you charge the paper for?
  7.  Draw a diagram to explain how the electrostatic motor works. Label each part and show where the charges are and how they make the rotor turn.

[/am4show]


Click here to go to next lesson on Alien Detector.

fet1This simple FET circuit is really an electronic version of the electroscope. This “Alien Detector” is a super-sensitive static charge detector made from a few electronics parts. I originally made a few of these and placed them in soap boxes and nailed the lids shut and asked kids how they worked. (I did place a on/off switch poking through the box along with the LED so they would have ‘some’ control over the experiment.)


This detector is so sensitive that you can go around your house and find pockets of static charge… even from your own footprints! This is an advanced project for advanced students.


You will need to get:


  • 9V battery clip (and a 9V battery)
  • MPF 102  (buy 2 – one for back up)
  • LED (any regular LED works fine)

[am4show have=’p9;p47;p76;p103;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]



Download Student Worksheet & Exercises


After you’ve made your charge detector, turn it on and comb your hair, holding the charge detector near your head and then the comb. You’ll notice that the comb makes the LED turn off, and your head (in certain spots) makes the LED go on. So it’s a positive charge static detector… this is important, because now you know when the LED is off, the space you’re detecting is negatively charged, and when it’s lit up, you’re in a pocket of positively charged particles. How far from the comb does your detector need to be to detect the charge? Does it matter how humid it is?


You can take your detector outdoors, away from any standing objects like trees, buildings, and people, and hold it high in the air. What does the LED look like? What happens when you lower the detector closer to the ground? Raise it back up again to get a second reading… did you find that the earth is negative, and the sky is more positive?


You can increase the antenna sensitivity by dangling an extra wire (like an alligator clip lead) to the end of the antenna. Because thunderstorms are moving electrical charges around (negative charges downwards and positive charges upwards), the earth is electrified negatively everywhere. During a thunderstorm, the friction caused by the moving water molecules is what causes lightning to strike! (But don’t test your ideas outside in the wide open while lightening is striking!)


Exercises


  1. When the LED is on, what do you think it means?
  2. Does the LED turning off detect anything?
  3. Do aliens like humidity?
  4. How does this alien detector really work?

[/am4show]


Click here to go to next lesson on Lightning.

What causes lightning, and how can we protect ourselves from strikes? In many textbooks, you’ll read about how clouds become electrically charged through friction in the moist air, but the truth is, scientists still don’t fully understand how and why lightning happens the way it does. But here’s what we do know: lightning happens when the positive and negative charges in a cloud become polarized. That is, the (extra) positive charges move to the top of the cloud and the (extra) negative charges move to the bottom of the cloud, usually by friction of the water vapor molecules in the cloud.


As the water molecules rise, electrons are stripped off and add to the charge of the cloud. The cloud can become ever more polarized if the rising water vapor freezes. The frozen particles clump together and take on a negative charge inside, positive charge on the outside, which rips the clumps apart to further polarize the cloud. The more polarized the cloud is, the more its electric field affects the space around it. The electrons on the surface of the Earth underneath the cloud are repelled by the bottom of the cloud, which creates a positive charge on the surface under the cloud. Trees. houses, cars, and people take on a positive charge as the cloud passes by.  Now we’re set up for a lightning strike.


[am4show have=’p9;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]



Even though a bolt of lightning can have 10 coulombs of charge, a coin contains about 250,000 coulombs of positive charge (balanced by the same amount of negative charge). There is a whole lot of electric charge that is in ordinary matter, but since it’s balanced, it’s not as noticeable as the lightning strike!


Yay! You’ve completed this set of lessons! Now it’s your turn to do physics problems on your own.


Download your Static Electricity Problem Set here.

[/am4show]


The way charges attract or repel each other can be described as a force. A charge can exert a push or pull on another charge depending on if the charges are positive or negative. How much force they exert can be figured out using Coulomb’s Law of Electric Force, which is:



where  C = 8.99 x 109 Nm2/C2


[am4show have=’p9;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]


Now Coulomb’s Law looks a lot like Newton’s Law of Gravitation… they both have a constant out in front, and they both have the inverse square relationship relating distance to force. They are different, however in a couple of important ways. Newton’s Law of Gravitation breaks down on the atomic level, and has to be replaced with Quantum Mechanics. Also, gravity is only an attractive force, whereas electric forces are both attractive and repulsive.



 


Notice the inverse square relationship: if you double the distance two charges are standing apart, the electrical force felt by the charges will decrease by a factor of four. If you triple the distance, the force goes down by a factor of nine.


Teachers and students both like to study, teach and learn subjects in neat, separate little packages, but this isn’t the way the universe works. Things aren’t usually isolated in their own box so they nothing to do with anything else. When we learned about the inverse square law, it wasn’t only for Newton’s Law of Gravitation… it popped up here also! And Newton’s Laws included forces, acceleration, gravity and energy, and now we’re going to add in an electrical force. But what does electrical force have to do with Newton’s Laws?


Click here to go to next lesson on Coulomb’s Law and Newton’s Laws.

[/am4show]


You can’t do an experiment on the planet without gravity playing some part of it (albeit sometimes so small you can ignore gravitational effects) since we’re in the Earth’s gravitational field. The electrical forces will add another force vector to our FBD that can be used when we look at how objects move in reaction to the forces.


Let’s take a look at how this works:


[am4show have=’p9;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]



 


Click here to go to next lesson on Charges in Objects.

[/am4show]


How much charge do you think is inside a penny? What would happen if you could separate the positive and negative charges? How much force would each bundle of charge experience? Here’s how you find out:


[am4show have=’p9;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]



 


Click here to go to next lesson on Forces in an Atom.

[/am4show]


As a physics student, I wondered how much of a pulling force was between the nucleus of an atom and the electrons. Let’s look at the simplest atom (hydrogen) and find the attractive force between the proton and the electron:


[am4show have=’p9;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]



 


Click here to go to next lesson on Why do Protons Stick Together Inside the Nucleus?

[/am4show]


Wasn’t that incredible how much force was present just between the two? After I figured that out, I wanted to know how much “push” was present between two protons in the nucleus. If you think about it, there’s really no reason for the protons to stick together inside the nucleus because they are all positively charged. Let’s take a look at the iron atom as we figure this out…


[am4show have=’p9;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]



There are four types of forces. They are, in order of strength: the strong nuclear force, electromagnetism, weak nuclear force, and gravity. That’s it. Those are all the forces that do all the pushing and pulling in the entire universe. The strong and weak nuclear forces are responsible for holding atoms together. They are quite important as you can imagine!


What kind of forces do protons inside the nucleus of an atom experience?  They are both positive charges, and really they don’t have any reason to stay together inside the nucleus as they’d be experiecing a repulsive force with each other. Let’s see exactly how big this repulsive force is:



 
Of all the forces, gravity is the weakling. It is actually much weaker than the other three. (In fact, in a way the other three have a tendency to pick on gravity, which isn’t very nice.)


Click here to go to next lesson on Electric Fields.

[/am4show]


[am4show have='p8;p9;p76;p20;p47;p97;p58;' guest_error='Guest error message' user_error='User error message' ] How are charges created? And how much? There's a scientific way to measure it.
  And what about lightning? How does that work when it comes to static charge?
    This is a recording of a recent live teleclass I did with thousands of kids from all over the world. I've included it here so you can participate and learn, too! We're going to study electrons and static charge. Kids will build simple electrostatic motor to help them understand how like charges repel and opposites attract. After you've completed this teleclass, be sure to hop on over the teleclass in Robotics! Electrons are strange and unusual little fellows. Strange things happen when too many or too few of the little fellows get together. Some things may be attracted to other things or some things may push other things away. Occasionally you may see a spark of light and sound. The light and sound may be quite small or may be as large as a bolt of lightning. When electrons gather, strange things happen. Those strange things are static electricity. Materials:
  • Balloon (7-9", inflated with air, not helium)
  • AA battery case
  • 2 AA batteries for your battery case (cheap dollar-store “heavy duty” type are perfect. Don't use alkaline batteries if you can help it, because kids are going to short circuit their circuits, and the cheaper kind are safer in case they do.)
  • 1-2 LEDs
  • Alligator wires
  • 1.5-3V DC motor
  • 3-6V buzzer
If you want to make the laser burglar alarm, then get these also:
  • OPTIONAL: CdS Photoresistor for the laser burglar alarm
  • OPTIONAL: 9V Battery for laser burglar alarm
  • OPTIONAL: Laser pointer (the cheap kind from the dollar store work great) or strong flashlight for the laser burglar alarm
If you want to make the first robotics projects then also get these:
  • OPTIONAL: block of foam (any kind will do that is at least 2" on each side)
  • OPTIONAL: 10 (or more) wood skewers at least 4" long
  • OPTIONAL: 1 wood clothespin
  • OPTIONAL: Hot glue and glue sticks (with adult help)
If you want to make the second robotics project then also get these:
  • OPTIONAL: Additional 3V DV motor (you need two for this project)
  • OPTIONAL: 6 large popsicle sticks (tongue depressor size)
  • OPTIONAL: Tack or other sharp object for poking holes
  • OPTIONAL: Hot glue and glue sticks (with adult help)
 
 

Key Concepts

The proton has a positive charge, the neutron has no charge (neutron, neutral get it?) and the electron has a negative charge. These charges repel and attract one another kind of like magnets repel or attract. Like charges repel (push away) one another and unlike charges attract one another. Generally things are neutrally charged. They aren't very positive or negative, rather have a balance of both. Things get charged when electrons move. Electrons are negatively charged particles. So if an object has more electrons than it usually does, that object would have a negative charge. If an object has less electrons than protons (positive charges), it would have a positive charge. How do electrons move? It turns out that electrons can be kind of loosey goosey. Depending on the type of atom they are a part of, they are quite willing to jump ship and go somewhere else. The way to get them to jump ship is to rub things together. Like in our experiment we're about to do...

What's Going On?

In static electricity, electrons are negatively charged and they can move from one object to another. This movement of electrons can create a positive charge (if something has too few electrons) or a negative charge (if something has too many electrons). It turns out that electrons will also move around inside an object without necessarily leaving the object. When this happens the object is said to have a temporary charge. When you rub a balloon on your head, the balloon is now filled up with extra electrons, and now has a negative charge. Opposite charges attract right? So, is the entire yardstick now an opposite charge from the balloon? No. In fact, the yardstick is not charged at all. It is neutral. So why did the balloon attract it? The balloon is negatively charged. It created a temporary positive charge when it got close to the yardstick. As the balloon gets closer to the yardstick, it repels the electrons in the yardstick. The negatively charged electrons in the yardstick are repelled from the negatively charged electrons in the balloon. Since the electrons are repelled, what is left behind? Positive charges. The section of yardstick that has had its electrons repelled is now left positively charged. The negatively charged balloon will now be attracted to the positively charged yardstick. The yardstick is temporarily charged because once you move the balloon away, the electrons will go back to where they were and there will no longer be a charge on that part of the yardstick. This is why plastic wrap, Styrofoam packing popcorn, and socks right out of the dryer stick to things. All those things have charges and can create temporary charges on things they get close to.

Questions to Ask

  1. Does the shape of the balloon matter? Does hair color matter?
  2. What happens if you rub the balloon on other things, like a wool sweater?
  3. If you position other people with charged balloons around the table, can you keep the yardstick going?
  4. Can we see electrons?
  5. How do you get rid of extra electrons?
  6. Rub a balloon on your head, and then lift it up about 5 inches. Why is the hair attracted to the balloon?
  7. Why does the hair continue to stand on end after the balloon is taken away?
  8. Why do you think the yardstick moved?
  9. What other things are attracted or repelled the same way by the balloon? (Hint: try a ping pong ball.)
[/am4show]

Click here to go to next lesson on Triboelectric series.

 

The Triboelectric Effect is a type of electrification that happens when you rub two different materials together and then separate them. Often, one will take on a positive charge and the other a negative. But how do you know which is going to be which?


[am4show have=’p8;p9;p20;p47;p76;p97;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]



A bolt of lightning carries a LOT of extra excess electrons. We can calculate how much using a simple calculation.



No matter how hard you try, if you hae a copper rod that you rub with a cloth, you just can’t get a charge to build up on it. Why is that?



[/am4show]


Click here to go to next lesson on Electrostatic Motors.

You can use the idea that like charges repel (like two electrons) and opposites attract to move stuff around, stick to walls, float, spin, and roll. Make sure you do this experiment first.


I’ve got two different videos that use positive and negative charges to make things rotate, the first of which is more of a demonstration (unless you happen to have a 50,000 Volt electrostatic generator on hand), and the second is a homemade version on a smaller scale.


Did you know that you can make a motor turn using static electricity? Here’s how:


[am4show have=’p8;p9;p20;p47;p76;p97;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]



Download Student Worksheet & Exercises


Here’s how the electrostatic machine works – you will need:


  • a yardstick
  • spoon
  • balloon


How does it work? Different parts of the atom have different electrical charges. The proton has a positive charge, the neutron has no charge (neutron, neutral get it?) and the electron has a negative charge. These charges repel and attract one another kind of like magnets repel or attract. Like charges repel (push away) one another and unlike charges attract one another.


So if two items that are both negatively charged get close to one another, the two items will try to get away from one another. If two items are both positively charged, they will try to get away from one another. If one item is positive and the other negative, they will try to come together.


How do things get charged? Generally things are neutrally charged. They aren’t very positive or negative. However, occasionally (or on purpose as we’ll see later) things can gain a charge. Things get charged when electrons move. Electrons are negatively charged particles. So if an object has more electrons than it usually does, that object would have a negative charge. If an object has less electrons than protons (positive charges), it would have a positive charge.


How do electrons move? It turns out that electrons can be kind of loosey-goosey. Depending on the type of atom they are a part of, they are quite willing to jump ship and go somewhere else. The way to get them to jump ship is to rub things together.


Remember, in static electricity, electrons are negatively charged and they can move from one object to another. This movement of electrons can create a positive charge (if something has too few electrons) or a negative charge (if something has too many electrons). It turns out that electrons will also move around inside an object without necessarily leaving the object. When this happens the object is said to have a temporary charge.


Try this: Blow up a balloon. When you rub the balloon on your head, the balloon is now filled up with extra electrons, and now has a negative charge. Now stick it to a wall— to create a temporary charge on a wall.


Opposite charges attract right? So, is the entire wall now an opposite charge from the balloon? No. In fact, the wall is not charged at all. It is neutral. So why did the balloon stick to it?


The balloon is negatively charged. It created a temporary positive charge when it got close to the wall. As the balloon gets closer to the wall, it repels the electrons in the wall. The negatively charged electrons in the wall are repelled from the negatively charged electrons in the balloon.


Since the electrons are repelled, what is left behind? Positive charges. The section of wall that has had its electrons repelled is now left positively charged. The negatively charged balloon will now “stick” to the positively charged wall. The wall is temporarily charged because once you move the balloon away, the electrons will go back to where they were and there will no longer be a charge on that part of the wall.


This is why plastic wrap, Styrofoam packing popcorn, and socks right out of the dryer stick to things. All those things have charges and can create temporary charges on things they get close to.


Want to purchase an electrostatic machine? Here’s a link to the one used in the video called a Wimshurst Machine which makes sparks up to 4″ long. For younger kids, we recommend this fun hand-held, non-shocking electrostatic generator.


Exercises


  1.  What happens if you rub the balloon on other things, like a wool sweater?
  2.  If you position other people with charged balloons around the table, how long can you keep  the yardstick going
  3.  Can we see electrons?
  4.  How do you get rid of extra electrons?
  5.  Why do you think the yardstick moved?
  6.  What would happen if you use both a positively charged object and a negatively charged  object to make the yardstick move?

[/am4show]


Click here to go to next lesson on Coulomb’s Law.

Induction is another way to create a charge in an object. You can charge an object by induction without even touching it. I’ve got a couple of really neat experiments that will show you how this works, but here’s the basic idea: when you have two metal objects, like two soda cans, standing upright on a foam slab and just touching each other (so they are insulated from the table but in contact with each other), you can bring a charged balloon close to one of them and see a really interesting effect: the can closest to the charged balloon (which has a negative charge) will take on a positive charge, and the soda can furthest from the balloon will take on a negative charge. And when you separate the two cans, the charges on each will be evenly distributed over the surface of each can and remain polarized (the further can keeps its negative charge and the closer can keeps its positive charge). That’s charging by induction!


[am4show have=’p9;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]






Note that the net charge of the system was zero when you started, and is still zero when you finish, even though the electrons have moved and the charge on each can is different than when you started. Charge cannot be created or destroyed, however it can be transferred from one object to another by electrons. If you touch the soda can while you’re charging it, the electrons will enter your hand and “go to ground” and discharge your system. Humidity also does this using water vapor – the water molecules will dissipate your static charge build up so it looks like your static electricity experiments don’t work! However, if you bring a positively charged object near the soda cans and then touch the can, electrons will be attracted and actually create a larger static charge on the can.


This idea of “grounding” simply means that the excess charge (either positive or negative) can be removed by transferring electrons from something really big, like the Earth, that acts like a huge ocean of electrons.


Click here to go to next lesson on Electroscope.

[/am4show]


When high energy radiation strikes the Earth from space, it’s called cosmic rays. To be accurate, a cosmic ray is not like a ray of sunshine, but rather is a super-fast particle slinging through space. Think of throwing a grain of sand at a 100 mph… and that’s what we call a ‘cosmic ray’. Build your own electroscope with this video!


[am4show have=’p8;p9;p17;p44;p76;p90;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]
Materials:


  • Clean glass jar with a lid
  • Wire coat hanger and sand paper
  • Aluminum foil
  • Vice grips or a hacksaw
  • Scissors
  • Balloon or other object to create a static charge
  • Hot glue gun (optional)


Download Student Worksheet & Exercises


Troubleshooting: This device is also known as an electroscope, and its job is to detect static charges, whether positive or negative.  The easiest way to make sure your electroscope is working is to rub your head with a balloon and bring it near the foil ball on top – the foil “leaves” inside the jar should spread apart into a V-shape.


Exercises


  1. How does this detector work?
  2. Do all particles leave the same trail?
  3. What happens when the magnet is brought close to the jar?

[/am4show]


Jupiter not only has the biggest lightning bolts we’ve ever detected, it also shocks its moons with a charge of 3 million amps every time they pass through certain hotspots. Some of these bolts are cause by the friction of fast-moving clouds. Today you get to make your own sparks and simulate Jupiter’s turbulent storms.


Electrons are too small for us to see with our eyes, but there are other ways to detect something’s going on. The proton has a positive charge, and the electron has a negative charge. Like charges repel and opposite charges attract.


Materials


  • Foam plate
  • Foam cup
  • Wool cloth or sweater
  • Plastic baggie
  • Aluminum pie pan
  • Aluminum foil
  • Film canister or M&M container
  • Nail (needs to be a little longer than the film canister)
  • Hot glue gun or tape
  • Water

[am4show have=’p8;p9;p17;p44;p90;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]



Download Student Worksheet & Exercises


  1. Lay the aluminum pie pan in front of you, right-side up.
  2. Glue the foam cup to the middle of the inside of the pan.
  3. Lay the plate on the table, upside down. Place the pie pan (don’t glue it!) on top of the plate, back-to-back. Set aside.
  4. Insert the nail through the middle of the film canister lid. Wrap the bottom of the film canister with aluminum foil. Tape the foil into place.
  5. Fill the canister nearly full of water.
  6. Snap on the lid, making sure that the nail touches the water.
  7. Rub the foam plate with the wool for at least a minute to really charge it up. Place the plate upside down carefully on the table.
  8. Put the pie pan back on top of the foam plate. The plate has taken on the charge from the foam plate.
  9. Touch the pie pan with a finger… did you feel anything?
  10. Use the cup as a handle and lift the pie pan up.
  11. Touch the pan with your finger, and you should feel and see a spark (turn down the lights to make the room dark).
  12. Charge the foam plate again and set the pie pan back on top to charge it up. (Make sure you’re lifting the pie pan only by the foam cup, or you’ll discharge it accidentally.)
  13. Hold the film canister by the aluminum foil and touch the charged pie pan to the nail.
  14. Rub the foam plate with the wool again to charge it up. Set the pie pan on the foam plate to charge the pan. Now lift the pie pan and touch the pan to the nail. Do this a couple of times to really get a good charge in the film canister.
  15. Discharge the film canister by touching the foil with one finger and the nail with the other. Did you see a spark?
  16. The wool gives the plate a negative charge. You can use a plastic bag instead of the wool to give the foam plate a positive charge.

What’s Going On?

If you rub a balloon on your head, the balloon becomes filled up with extra electrons, and now has a negative charge. Try the following experiment to create a temporary charge on a wall: Bring the balloon close to the wall until it sticks.


Opposite charges attract right? So, is the entire wall now an opposite charge from the balloon? No. In fact, the wall is not charged at all. It is neutral. So why did the balloon stick to it?


The balloon is negatively charged. It created a temporary positive charge when it got close to the wall. As the balloon gets closer to the wall, it repels the electrons in the wall. The negatively charged electrons in the wall are repelled from the negatively charged electrons in the balloon.


Since the electrons are repelled, what is left behind? Positive charges. The section of wall that has had its electrons repelled is now left positively charged. The negatively charged balloon will now “stick” to the positively charged wall. The wall is temporarily charged because once you move the balloon away, the electrons will go back to where they were and there will no longer be a charge on that part of the wall.


This is why plastic wrap, Styrofoam packing popcorn, and socks right out of the dryer stick to things. All those things have charges and can create temporary charges on things they get close to.


If you rub a balloon all over your hair, the Triboelectric Effect causes the electrons to move from your head to the balloon. But why don’t the electrons go from the balloon to your head? The direction of electron transfer has to do with the properties of the material itself. And the balloon-hair combination isn’t the only game in town.


Electrons move differently depending on the materials that are rubbed together. A balloon takes on a negative charge when rubbed on hair. Today, the kids are going to find when a foam plate is rubbed with wool, the plate takes on electrons and creates a negative charge on the plate. To give the plate a positive charge, kids can rub it with a plastic bag.


The Triboelectric Series is a list that ranks different materials according to how they lose or gain electrons. A rubber rod rubbed with wool produces a negative charge on the rod, however an acrylic rod rubbed with silk creates a positive charge on the rod. A foam plate often has a positive charge when you slide one off the stack, but if you rub it with wool it will build up a negative charge.


Near the top of the list are materials that take on a positive charge, such as air, human skin, glass, rabbit fur, human hair, wool, silk, and aluminum. Near the bottom of the list are materials that take on a negative charge, such as amber, rubber balloons, copper, brass, gold, cellophane tape, Teflon, and silicone rubber. Scientists developed this list by doing a series of experiments, very similar to the ones we’re about to do.


Exercises


  1. What happens if you hold the nail and charge the aluminum foil?
  2. Can you see electrons? Why or why not?

[/am4show]


Click here to go to next lesson on Easy Photoelectric Effect Experiment

Photoelectric EffectEinstein received a Nobel Prize for figuring out what happens when you shine blue light on a sheet of metal.  When he aimed a blue light on a metal plate, electrons shot off the surface. (Metals have electrons which are free to move around, which is why metals are electrically conductive. More on this in Unit 10).


When Einstein aimed a red light at the metal sheet, nothing happened.  Even when he cranked the intensity (brightness) of the red light, still nothing happened.  So it was the energy of the light (wavelength), not the number of photons (intensity) that made the electrons eject from the plate. This is called the ‘photoelectric effect’. Can you imagine what happens if we aim a UV light (which has even more energy than blue light) at the plate?


This photoelectric effect is used by all sorts of things today, including solar cells, electronic components, older types of television screens, video camera detectors, and night-vision goggles.


This photoelectric effect also causes the outer shell of orbiting spacecraft to develop an electric charge, which can wreck havoc on its internal computer systems.


A surprising find was back in the 1960s, when scientists discovered that moon dust levitated through the photoelectric effect. Sunlight hit the lunar dust, which became (slightly) electrically charged, and the dust would then lift up off the surface in thin, thread-like fountains of particles up ¾ of a mile high.


[am4show have=’p8;p9;p97;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]


Materials:


  • soda or steel can
  • paper clip
  • sand paper
  • tinsel (or aluminum foil and scissors)
  • tape
  • foam cup
  • PVC pipe (any size)
  • brown paper bag
  • UV shortwave lamp (sometimes called a “germ-free portable lamp”)


[/am4show]


Click here to go to next lesson on Charging by Induction and Conduction.

Ygou can also charge objects by conduction. You’ve actually already done with without really thinking about it. The foil on the wire coat hanger in the electroscope was being charged by conduction. When you touch a charged balloon to the foil ball on the electroscope, that’s a charge by conduction. If you were to get the charged balloon really close but not touching the foil ball, that would be charging by induction. (See the difference?) Charging by conduction just means that you need to touch the electrically neutral object to the one that is charged to transfer the charge. It’s charge by contact.


With charge by induction, it’s the forces due to likes repelling and opposites attracting that cause the charge in objects. With conduction, it’s the actual movement of electrons to the object that make the charge in the object. This is obvious if you think about touching two soda cans together, since they are both made out of a material that allows electrons to move about freely within the material (on the surface of the object). But what about two insulators, like two foam plates? What happens then?


[am4show have=’p9;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]



Insulators do not conduct charge the way that conductors do. Even if two foam plates are touching, charge can not be conducted from one foam plate to another, or even from a foam plate to a soda can. However the foam plate can polarize the soda can through electrical forces (opposite charges attracting and lie charges repelling).


Click here to go to next lesson on Electric Force.

[/am4show]


This experiment is just for advanced students. If you guessed that this has to do with electricity and chemistry, you’re right! But you might wonder how they work together. Back in 1800, William Nicholson and Johann Ritter were the first ones to split water into hydrogen and oxygen using electrolysis. (Soon afterward, Ritter went on to figure out electroplating.) They added energy in the form of an electric current into a cup of water and captured the bubbles forming into two separate cups, one for hydrogen and other for oxygen.


This experiment is not an easy one, so feel free to skip it if you need to. You don’t need to do this to get the concepts of this lesson but it’s such a neat and classical experiment (my students love it) so you can give it a try if you want to. The reason I like this is because what you are really doing in this experiment is ripping molecules apart and then later crashing them back together.


Have fun and please follow the directions carefully. This could be dangerous if you’re not careful. The image shown here is using graphite from two pencils sharpened on both ends, but the instructions below use wire.  Feel free to try both to see which types of electrodes provide the best results.


[am4show have=’p9;p40;p76;p91;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]


You will need:


  • 2 test tubes or thin glass or plastic something closed at one end. I do not recommend anything wider than a half inch in diameter.
  • 2 two wires, one needs to be copper, at least 12 inches long. Both wires need to have bare ends.
  • 1 Cup
  • Water
  • One 9 volt battery
  • Long match or a long thin piece of wood (like a popsicle stick) and a match
  • Rubber bands
  • Masking tape
  • Salt


Download Student Worksheet & Exercises
1. Fill the cup with water.


2. Put a tablespoon or so of salt into the water and stir it up. (The salt allows the electricity to flow better through the water.)


2. Put one wire into the test tube and rubber band it to the test tube so that it won’t come out (see picture).


3. Use the masking tape to attach both wires to the battery. Make sure the wire that is in the test tube is connected to the negative (-) pole of the battery and that the other is connected to the positive (+) pole. Don’t let the bare parts of the different wires touch. They could get very hot if they do.


4. Fill the test tube to the brim with the salt water.


5. This is the tricky part. Put your finger over the test tube, turn it over and put the test tube, open side down, into the cup of water. (See picture.)


6. Now put the other wire into the water. Be careful not to let the bare parts of the wires touch.


7. You should see bubbles rising into the test tube. If you don’t see bubbles, check the other wire. If bubbles are coming from the other wire either switch the wires on the battery connections or put the wire that is bubbling into the test tube and remove the other. If you see no bubbles check the connections on the battery.


8. When the test tube is half full of gas (half empty of salt water depending on how you look at it) light the long match or the wooden stick. Then take the test tube out of the water and let the water drain out. Holding the test tube with the open end down, wait for five seconds and put the burning stick deep into the test tube (the flame will probably go out but that’s okay). You should hear an instant pop and see a flash of light. If you don’t, light the stick again and try it another time. For some reason, it rarely works the first time but usually does the second or third.


A water molecule, as you saw before, is two hydrogen atoms and one oxygen atom. The electricity encouraged the oxygen to react with the copper wire leaving the hydrogen atoms with no oxygen atom to hang onto. The bubbles you saw were caused by the newly released hydrogen atoms floating through the test tube in the form of hydrogen gas. Eventually that test tube was part way filled with nothing but pure hydrogen gas.


But how do you know which bubbles are which? You can tell the difference between the two by the way they ignite (don’t’ worry – you’re only making a tiny bit of each one, so this experiment is completely safe to do with a grown up).


It takes energy to split a water molecule. (On the flip side, when you combine oxygen and hydrogen together, it makes water and a puff of energy. That’s what a fuel cell does.) Back to splitting the water molecule – as the electricity zips through your wires, the water molecule breaks apart into smaller pieces: hydrogen ions (positively charged hydrogen) and oxygen ions (negatively charged oxygen). Remember that a battery has a plus and a minus charge to it, and that positive and negative attract each other.


So, the positive hydrogen ions zip over to the negative terminal and form tiny bubbles right on the wire. Same thing happens on the positive battery wire. After a bit of time, the ions form a larger gas bubble. If you stick a cup over each wire, you can capture the bubbles and when you’re ready, ignite each to verify which is which.


If the match burns brighter, the gas is oxygen. If you hear a POP!, the gas is hydrogen. Oxygen itself is not flammable, so you need a fuel in addition to the oxygen for a flame. In one case, the fuel is hydrogen, and hence you hear a pop as it ignites. In the other case, the fuel is the match itself, and the flame glows brighter with the addition of more oxygen.


When you put the match to it, the energy of the heat causes the hydrogen to react with the oxygen in the air and “POP”, hydrogen and oxygen combine to form what? That’s right, more water. You have destroyed and created water! (It’s a very small amount of water so you probably won’t see much change in the test tube.)


The chemical equations going on during this electrolysis process look like this:


A reduction reaction is happening at the negatively charged cathode. Electrons from the cathode are sticking to the hydrogen cations to form hydrogen gas:


2 H+(aq) + 2e –> H2(g)


2 H2O(l) + 2e –> H2(g) + 2 OH(aq)


The oxidation reaction is occurring at the positively charged anode as oxygen is being generated:


2 H2O(l)  –> O2(g) + 4 H+(aq) + 4e


4 OH(aq) –> O2(g) + 2 H2O(l) + 4 e-


Overall reaction:


2 H2O(l)  –> 2 H2(g) + O2(g)


Note that this reaction creates twice the amount of hydrogen than oxygen molecules. If the temperature and pressure for both are the same, you can expect to get twice the volume of hydrogen to oxygen gas (This relationship between pressure, temperature, and volume is the Ideal Gas Law principle.)


This is the idea behind vehicles that run on sunlight and water.  They use a solar panel (instead of a 9V battery) to break apart the hydrogen and oxygen and store them in separate tanks, then run them both back together through a fuel cell, which captures the energy (released when the hydrogen and oxygen recombine into water) and turns the car’s motor. Cool, isn’t it?


Note: We’re going to focus on Alternative Energy in Unit 12 and create all sorts of various energy sources including how to make your own solar battery, heat engine, solar & fuel cell vehicles (as described above), and more!


Exercises


  1. Why are bubbles forming?
  2. Did bubbles form at both wires, or only one? What kind of bubbles are they?
  3. What would happen if you did this experiment with plain water? Would it work? Why or why not?
  4. Which terminal (positive or negative) produced the hydrogen gas?
  5. Did the reaction create more hydrogen or more oxygen?

[/am4show]


Click here to go to next lesson on Molecules and Atoms.

Oxygen Atomic Diagram

Let’s try another way to look at this. You’re playing miniature golf and you come to the old wind mill hole. Your friend takes a shot and since the blades of the windmill are going nice and slow he gets the ball right through. Now it’s your turn. Suddenly you hear a zap and a pow and sparks go flying. Something has gone wrong with the wind mill and it starts spinning at amazing speeds. You decide to give it a try and hit the ball towards the wind mill.


Well since it is spinning out of control, those blades now form almost a solid disk so that there is no way your ball can get through the wind mill. Electrons do the same thing. They move so fast that even though there may not be many of them, they form a shell that can’t be penetrated. (To be clear, particles that are smaller than an atom can go through the shells and pop out the other side.)



Let’s go a little further with this shell thing. An atom can have as few as one and as many as seven shells. Imagine our balloon again. Now there can be a balloon inside of a balloon inside a balloon and so on. Up to seven balloons! Each balloon, whoops, I mean shell, can have only so many electrons in it. This simple equation 2n2 tells you how many electrons can be in each shell. The n stands for the number of the shell.


The first shell can have up to 2 x 1(first shell)2 or 2 electrons. The second shell can have up to 2 x 2(second shell)2 or 8 electrons. The third shell can have up to 2 x 32 or 18 electrons. The fourth shell can have up to 2 x 42 or 32 electrons. All the way up to the seventh shell which can have 2 x 72 or 98 electrons!


One last thing about shells, the shells have to be full before the electrons will go to the next shell. A helium atom will have two electrons. Both of them will be in the first shell. A Lithium atom will have three electrons. Two will be in the first shell and one (since the first shell is filled) will be in the second shell.


Electrons provide the size and stability of the atom and, as such, the mass and the structure of all matter. Electrons are also the key to all electromagnetic energy. But wait, that’s not all! It is the number of electrons in an atom that determines if and how atoms come together to form molecules. Electrons determine how and what matter will be.


Atoms like to feel satisfied and they feel satisfied if they are “full”.  An atom is “full” if its outer electron shell has as many electrons as it can hold or if there are eight or a multiple of eight (16, 24 etc.) electrons in the outer shell. This is called the octet rule and works most of the time, but is not perfect.


If an atom is not full, it is not satisfied. An unsatisfied atom needs to do something with its electrons to be happy. Luckily atoms are very friendly and love to share. Most atoms are not satisfied as individuals. The oxygen atom has six electrons in its outer shell. It needs eight electrons to be satisfied.


Luckily, two Hydrogen atoms happen by. Each one of them has only one electron in its outer shell and needs one more to be satisfied. If both Hydrogens share their one electron with the Oxygen, the oxygen has eight electrons and is satisfied. Also, if the Oxygen shares an electron with each Hydrogen, then both Hydrogens are satisfied as well. Just like your mother told you, it’s nice to share. It is this sharing of electrons that makes atoms come together to form molecules.


Click here to go to next lesson on Electrostatic Charge.

[/am4show]


To summarize, protons and neutrons are in the nucleus of an atom, and tightly bound together. The proton has a positive charge while the neutron has no charge, and both of them are much larger than the electron. The tiny electron is outside the nucleus and weakly bound to the atom and carries a negative a charge.


[am4show have=’p9;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]



Go get a balloon. The rubber latex kind work the best (not the shiny Mylar kind). You’ll need it for the next set of experiments we’re going to talk about below. When you rub a balloon on your head, you charge up the balloon with a negative static charge. But how much charge is it? The units of charge are called the Coulomb (C), just like the units of time are seconds (s). And just like seconds, you can have microseconds (10-6 seconds) and nanoseconds (10-9 seconds), you can have microCoulombs (10-6 C or μC) and nanoCoulombs (10-9 C or nC).


The charge of one electron is -1.6 x 10-19 C… it’s a really small number! The charge of one proton is +1.6 x 10-19 C. The kind of charge (whether positive or negative) is determined by how many extra protons or electrons are present in addition to the ones that are evenly matched to balance the charge. If an object has 15 protons and 17 electrons, then it’s got a negative charge by 2 electrons. Just because an object is not charged (electrically neutral) doesn’t mean it doesn’t have any protons or electrons. Rather it means that the number of electrons and protons are evenly matched to balance the charge of the object. We say that charge is quantized, which means that electric charge isn’t a continuous fluid flow, but instead is made up of tiny packets of charged particles. The charge on one electron is -1.60 x 10-19 C.  This is one of the most fundamental concepts in physics! 


Click here to go to next lesson on The Charge of Lightning.

[/am4show]


Let’s go back to rubbing a balloon on your head. When you do this and bring it close to objects like a thin stream of water trickling out of the faucet, or small its of paper, or bubbles in the air, or even a ping pong ball on the table, did you notice now you can influence things? You can make water flick and spray, paper jump up and down, and bubbles and ping pong balls will follow your every move. But why is that?


[am4show have=’p9;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]



 


Click here to go to next lesson on Maxwell’s First Equation.

[/am4show]


The influence you’re exerting on these objects is called the electric force,  which is a non-contact force that can happen over a distance.


[am4show have=’p9;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]



James Maxwell, a Scottish theoretical physicist who made important contributions to electromagnetic theory.
James Maxwell, a Scottish theoretical physicist who made important contributions to electromagnetic theory.

Did you notice that you can exert a force on an object without touching it? Try it now if you haven’t already! Did you notice how opposite charges attract and like charges repel? That’s the fundamental key concept with this section.  Electrical force are the attractive for opposite charges and repulsive for like charges. Electrical force is also attractive between a charged and a neutral object.


Click here to go to next lesson on Conductors and Insulators.

[/am4show]


An electrical circuit is like a NASCAR raceway.  The electrons (racecars) zip around the race loop (wire circuit) superfast to make stuff happen. Although you can’t see the electrons zipping around the circuit, you can see the effects: lighting up LEDs, sounding buzzers, clicking relays, etc.


There are many different electrical components that make the electrons react in different ways, such as resistors (limit current), capacitors (collect a charge), transistors (gate for electrons), relays (electricity itself activates a switch), diodes (one-way street for electrons), solenoids (electrical magnet), switches (stoplight for electrons), and more.  We’re going to use a combination diode-light-bulb (LED), buzzers, and motors in our circuits right now.


A CIRCUIT looks like a CIRCLE.  When you connect the batteries to the LED with wire and make a circle, the LED lights up.  If you break open the circle, electricity (current) doesn’t flow and the LED turns dark.


LED stands for “Light Emitting Diode”.  Diodes are one-way streets for electricity – they allow electrons to flow one way but not the other.


Remember when you scuffed along the carpet?  You gathered up an electric charge in your body.  That charge was static until you zapped someone else.  The movement of electric charge is called electric current, and is measured in amperes (A). When electric current passes through a material, it does it by electrical conduction. There are different kinds of conduction, such as metallic conduction, where electrons flow through a conductor (like metal) and electrolysis, where charged atoms (called ions) flow through liquids.


[am4show have=’p8;p9;p20;p47;p106;p76;p97;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]


Here’s what you need:


  • 2 AA batteries
  • AA battery case
  • 2 alligator wires
  • LEDs (any you choose is fine)


Download Student Worksheet & Exercises


Be alert for:


1. Batteries inserted into the case the wrong way!


2. LED in the wrong way (LEDs are picky about plus and minus – they are POLARIZED)


3. Is there a metal-to-metal connection?  (You’re not grabbing ahold of the plastic insulation, are you?)


4. Bad wires can cause headaches – if all else fails, then swap out your alligator clip lead wires for new ones.


Exercises


  1. What does LED stand for?
  2. Does it matter which way you wire an LED in a circuit?
  3. Does the longer wire on the LED connect to plus (red) or minus (black)?
  4. Do you need to hook up batteries to make a neon bulb light up?  Why or why not?
  5. What’s the difference between a light bulb and your LED?
  6. What is the difference between a bolt of lightning and the electricity in your circuit?
  7. What is the charge of an electron?

[/am4show]


Click here to go to next lesson on Why does metal conduct electricity?

switch-zoomMake yourself a grab bag of fun things to test: copper pieces (nails or pipe pieces), zinc washers, pipe cleaners, Mylar, aluminum foil, pennies, nickels, keys, film canisters, paper clips, load stones (magnetic rock), other rocks, and just about anything else in the back of your desk drawer.


Certain materials conduct electricity better than others. Silver, for example, is one of the best electrical conductors on the planet, followed closely by copper and gold. Most scientists use gold contacts because, unlike silver and copper, gold does not tarnish (oxidize) as easily. Gold is a soft metal and wears away much more easily than others, but since most circuits are built for the short term (less than 50 years of use), the loss of material is unnoticeable.
[am4show have=’p8;p9;p20;p47;p76;p97;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]


Modify your basic LED circuit into a Conductivity Circuit by removing one clip lead from the battery and inserting a third clip lead to the battery terminal. The two free ends are your new clips to put things in from the grab bag. Try zippers, metal buttons, barrettes, water from a fountain, the fountain itself, bike racks, locks, doorknobs, unpainted benches… you get the idea!


Here’s what you need:


  • 2 AA batteries
  • AA battery case
  • 3 alligator wires
  • LEDs (any you choose is fine)
  • paper clip
  • penny
  • other metal objects around your house (zippers, chairs, etc…)


Why does metal conduct electricity?

Why does metal, not plastic, conduct electricity? Imagine you have a garden hose with water flowing through it. The hose is like the metal wire, and the water is like the electric current. Trying to run electricity through plastic is like filling your hose with cement. It’s just the nature of the material.



Download Student Worksheet & Exercises


Exercises


  1.       Name six materials that are electrically conductive.
  2.        What kinds of materials are conductors and insulators?
  3.      Can you convert an insulator into a conductor? How?
  4.        Name four instances when insulators are a bad idea to have around.
  5.      When are insulators essential to have?

[/am4show]


Click here to go to next lesson on Liquid Conductors.

When an atom (like hydrogen) or molecule (like water) loses an electron (negative charge), it becomes an ion and takes on a positive charge. When an atom (or molecule) gains an electron, it becomes a negative ion. An electrolyte is any substance (like salt) that becomes a conductor of electricity when dissolved in a solvent (like water).


This type of conductor is called an ‘ionic conductor’ because once the salt is in the water, it helps along the flow of electrons from one clip lead terminal to the other so that there is a continuous flow of electricity.


This experiment is an extension of the Conductivity Tester experiment, only in this case we’re using water as a holder for different substances, like sugar and salt. You can use orange juice, lemon juice, vinegar, baking powder, baking soda, spices, cornstarch, flour, oil, soap, shampoo, and anything else you have around. Don’t forget to test out plain water for your ‘control’ in the experiment!


[am4show have=’p8;p9;p20;p47;p76;p91;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]


Here’s what you need:


  • 2 AA batteries
  • AA battery case
  • 2 alligator clips
  • LED
  • water
  • salt
  • glass jar (like a clean jam jar)


Download Student Worksheet & Exercises


Exercises


  1. Why does electricity flow through some solutions but not all of them?
  2. What is a salt?
  3. How are electrolytes used today in real life?
  4. Which substance was your top conductor?
  5. Which substance didn’t conduct anything at all?
  6. What happens if you mix an electrolyte and non-electrolyte together?

[/am4show]


Click here to go to next lesson on Superconductors.

When I was in 10th grade, my teammate and I designed what we thought was pretty clever: a superconductor roller coaster, which we imagined would float effortlessly above its magnetic track. Of course, our roller coaster was only designed on paper, because yttrium barium copper oxide ceramics had only just been discovered by top scientists.



Did you notice how it was smoking in the video? That’s because it was so cold! The usual problem with superconductors is that they need to be incredibly cold in order to exhibit superconductive properties.  Yttrium barium copper oxide (YBa2Cu3O7) was the first compound that used liquid nitrogen for cooling, making superconductors a lot less expensive to work with – you no longer needed a cryogenic lab in order to levitate objects above a magnet.



Recently, scientists have found a way to make an amazing superconductor by taking a single crystal sapphire wafer and coating it with a thin (~1µm thick) ceramic material (yttrium barium copper oxide). Normally, the ceramic layer has no interesting magnetic or electrical properties, but that’s when you’re looking at it at room temperature. If you cool this material below -185ºC (-301ºF), it turns out that the ceramic material becomes a superconductor, meaning that it conducts electricity without resistance, with no energy loss. Zero. That’s what makes it a ‘superconductor’.


To further understand superconductivity, it’s helpful to understand what normally happens to electricity as it flows through a wire. As you may know, energy cannot be created or destroyed, but can be changed from one form to another.


In the case of wires, some of the electrical energy is changed to heat energy. If you’ve ever touched a wire that had been in use for a while, and discovered it was hot, you’ve experienced this. The heat energy is a waste. It simply means that less electricity gets to its final destination.


This is why superconductivity is so cool (no pun intended.) By cooling things down to temperatures near absolute zero, which is as low as temperatures can get, you can create a phenomenon where electricity flows without having any of it converted to heat.


Why do superconductors float above magnets?

Scientists also figured out that superconductors and magnetic field really do not like each other. The Meissner effect happens when a superconductor expels all its magnetic fields from inside.


However, if you make your superconductor thin enough, you can get the magnetic field to penetrate in discrete quantities (this is real quantum physics now) called flux tubes (the blue lines that go through the disc).


Inside each of the magnetic flux tubes, the superconductivity is destroyed, but the superconductor tries to keep the magnetic tubes pinned in weak areas and any movement of the superconductor itself (like if you pushed it) causes the flux tubes to move, and this is what traps (or locks) the superconductor in midair.



If you’d like to experiment with superconductors yourself, check out this information.


Click here to go to next lesson on The difference between polarizing and charging.

Have you ever had a bad hair day? Did you happen to notice if the air was drier or wetter weather on those days? Usually folks have bad hair days when the air is drier, which is when static charge can build up more easily. Some folks notice every time they touch a doorknob, slide down a plastic slide, or scuff along the carpet in socks that they get zapped. Since there’s less water vapor in the air on drier days, there’s more of a chance for static charge to build up. The water molecule dissipates the static charge, and the more wet the air is (humid), the less static build up there is. Static electricity experiments are really hard to do on humid days, especially if it’s raining outside!
[am4show have=’p9;p58;’ guest_error=’Guest error message’ user_error=’User error message’ ]
Can you rub a balloon and stick it to the wall? Why does that work? The wall isn’t positively charged, is it?


No… the wall is not charged at all. It’s electrically neutral. However, when you bring a negatively charged balloon near it, two important things happen: the negative charge on the balloon repels the negative charges in the wall, pushing them further away. At the same time, the positive charges in the wall are attracted to the balloon and move toward it. The result is that the balloon sticks to the wall, and you have just moved charges around in the wall without even realizing it. Polarization means that you separate the charges in an object. The wall became polarized when you brought the balloon close to it.


Like charges repel and opposites attract.This happens in neutrally charged objects, like the yardstick in the electrostatic motor that you’ve done previously on this page. If the object is a conductor, like a metal, the charges move quickly from one side of the object to the other quite freely along the surface.


However if the object is an insulator, the electrons simply redistribute themselves within the atom, since the charges can’t move along the surface as they would with a conductor. The electrons live in an electron cloud that surrounds the nucleus of the atom, which normally is uniform and symmetrical. When an electrical charge is applied to insulators, that cloud will distort and become non-symmetrical as the electrons move in response.  In this way, insulators can be polarized.


Water is a polar molecule. In a molecule, the atoms stay together to form the molecule through bonds that are formed between the negative and positive charges on the individual atoms. For water, the oxygen  and hydrogen have a polar bond because the protons in one are attracted to the electrons in the other. The electrons are shared and their electron clouds overlap.


For water however, the electrons within the clouds are not equally shared which makes the electron cloud distorted, making one side of the water molecule more negatively electrically charged than the other. This makes water a polar molecule because the electron cloud is shifted more toward the oxygen than the hydrogen atoms.


When you bring a charged balloon near a thin trickle of water streaming from the faucet, the stream is deflected and sprayed by the presence of the balloon because the water molecules are polar and align to the balloon.


Just a quick tip: don’t mix up the concepts of polarizing and charging.  Charging is when there’s an imbalance of electric charge, like rubbing the balloon on your head. The balloon now has an excess number of electrons, so it’s negatively charged. Objects that are polarized have their charges separated either on the surface or within the atom itself. The overall charge of a polarized object is balanced (electrically neutral), even if the negative charges are at one end and positive charges are on the other.


Scientific Concepts for Atoms:


  • All matter is made of atoms.
  • An atom is the smallest part of stable matter.
  • Atoms rarely hang out alone. They join together in groups from two to millions of atoms.
  • Atoms are made of three basic particles. Neutrons, protons, and electrons.
  • Neutrons and protons are together in the middle of the atom and make up the nucleus of the atom. Electrons move around the nucleus. They don’t “orbit” the nucleus. Next lesson we will talk more about how they move. It’s one of the wacky things about electrons.
  • Atoms differ from one another by how many protons, neutrons, and electrons they have in them.
  • Elements are specific kinds of atoms. Every atom is a type of element.
  • There are over 112 elements. Ninety of which are found naturally. Twelve different elements are the major ingredients of over 90% of all matter. Five different elements are the major ingredients of all living things.
  • Carbon, Hydrogen, Oxygen, Nitrogen, and Calcium are the five main elements that make up all living matter.
  • Most atoms come from stars and have been around since the beginning of time.
  • Atoms get used, and reused again and again as things change over time.

Scientific Concepts for Electrons:


  • Electrons don’t orbit nuclei. They pop in and pop out of existence.
  • Electrons do tend to stay at a certain distance from a nucleus. This area that the electron tends to stay in is called a shell.
  • The electrons move so fast around the shell that the shell forms a balloon like ball around the nucleus.
  • An atom can have as many as seven shells.
  • The number of electrons an atom has determines how many shells it has.
  • A shell can only hold so many electrons. The number of electrons a shell can hold can be determined by the formula 2n2 where n is the number of the shell.
  • Atoms are “satisfied” if they have a full outer shell or if they have a multiple of eight electrons in their outer shell.
  • If an atom is not “satisfied” it will gladly share electrons with other atoms forming molecules.

Click here to go to next lesson on Charging Methods.

[/am4show]