Magic Water Glass Trick

Monday May 31, 2010

Where’s the pressure difference in this trick?


At the opening of the glass. The water inside the glass weighs a pound at best, and, depending on the size of the opening of the glass, the air pressure is exerting 15-30 pounds upward on the bottom of the card. Guess who wins? Tip, when you get good at this experiment, try doing it over a friend’s head!


Materials: a glass, and an index card large enough to completely cover the mouth of the glass.


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Fill a glass one-third with water. Cover the mouth with an index card and over a sink invert the glass while holding the card in place. Remove your hand from the card. Voila! Because atmospheric air pressure is pushing on all sides of both the glass and the card, the card defies gravity and “sticks” to the bottom of the glass. Recall that higher pressure pushes and when you have a difference in pressure, things move. This same pressure difference causes storms, winds, and the index card to stay in place.


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Hot Air Balloon

Monday May 31, 2010

About 400 years ago, Leonardo da Vinci wanted to fly… so he studied the only flying things around at that time: birds and insects. Then he did what any normal kid would do—he drew pictures of flying machines!


Centuries later, a toy company found his drawing for an ornithopter, a machine that flew by flapping its wings (unlike an airplane, which has non-moving wings). The problem (and secret to the toy’s popularity) was that with its wing-flapping design, the ornithopter could not be steered and was unpredictable: It zoomed, dipped, rolled, and looped through the sky. Sick bags, anyone?


Hot air balloons that took people into the air first lifted off the ground in the 1780s, shortly after Leonardo da Vinci’s plans for the ornithopter took flight. While limited seating and steering were still major problems to overcome, let’s get a feeling for what our scientific forefathers experienced as we make a balloon that can soar high into the morning sky.


Materials: A lightweight plastic garbage bag, duct or masking tape, a hand-held hair dryer. And a COLD morning.


Here’s what you do:


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Shake out a garbage bag to its maximum capacity. Using duct or masking tape, reduce the opening until it is almost-closed leaving only a small hole the size of the hair dryer nozzle. Use the hair dryer to inflate the bag, heating the air inside, but make sure you don’t melt the bag! When the air is at its warmest, release your hold on the bag while at the same time you switch off the hair dryer. The bag should float upwards and stay there for a while.


Troubleshooting: This experiment works best on cold, windless mornings. If it’s windy outside, try a cool room. The greater the temperature difference between the hot air inside the garbage bag versus the cold, still air, the faster the bag rises. The only other thing to watch for is that you’ve taped the mouth of the garbage bag securely so the hot air doesn’t seep out. Be sure the opening you leave is only the diameter of your hair dryer’s nozzle.


Want to go BIGGER? Then try the 60-foot solar tube!
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Diaper Wind Bag

Monday May 31, 2010

Lots of science toy companies will sell you this experiment, but why not make your own? You’ll need to find a loooooong bag, which is why we recommend a diaper genie. A diaper genie is a 25′ long plastic bag, only both ends are open so it’s more like a tube. You can get three 8-foot bags out of one pack.


Kids have a tendency to shove the bag right up to their face and blow, cutting off the air flow from the surrounding air into the bag. When they figure out this experiment and perform it correctly, this is one of those oooh-ahhh experiments that will leave your kids with eyes as big as dinner plates.


Here’s what you do:


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Cut an eight-foot section of the diaper genie bag and knot one of the ends. Hold the other end open, take a deep breath, and blow. How many breaths does it take for you to fill up the entire bag with air? Try this now…


After you know how many breaths it takes, do you think you can fill the bag with only ONE breath? The answer is YES! Hold the bag about eight inches from the face and blow long and steady into the bag. As soon as you run out of air, close the end of the bag and slide your hand along the length (toward the knotted end) until you have an inflated blimp.


Troubleshooting: If the bag tears open, use packing tape to mend it.


What’s going on? When you blow air past your lips, a pocket of lower air pressure forms in front of your face. The stronger you blow, the lower the air pressure pocket. The air surrounding this lower pressure region is now at a higher pressure than the surrounding air, which causes things to shift and move. When you blow into the bag (keeping the bag a few inches from your face), you build a lower pressure area at the mouth of the bag, and the surrounding air rushes forward and into the bag.


Substitution Tip: If you can’t locate a diaper genie, you can string together plastic sheets from garbage bags, using lightweight tape to secure the seams. You’ll need to make a 8-12” diameter by eight-foot long tube and close one end. When kids get their eight-foot bag inflated in just one breath, ask them: “Did you really have that much air in your lungs?”


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Genie in a Bottle

Monday May 31, 2010

While this isn’t actually an air-pressure experiment but more of an activity in density, really, it’s still a great visual demonstration of why Hot Air Balloons rise on cold mornings.


Imagine a glass of hot water and a glass of cold water sitting on a table, side by side. Now imagine you have a way to count the number of water molecules in each glass. Which glass has more water molecules?


The glass of cold water has way more molecules… but why? The cold water is more dense than the hot water. Warmer stuff tends to rise because it’s less dense than colder stuff and that’s why the hot air balloon in experiment 1.10 floated up to the sky.


Clouds form as warm air carrying moisture rises within cooler air. As the warm, wet air rises, it cools and begins to condense, releasing energy that keeps the air warmer than its surroundings. Therefore, it continues to rise. Sometimes, in places like Florida, this process continues long enough for thunderclouds to form. Let’s do an experiment to better visualize this idea.


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Materials: Two identical tall glasses, hot water, cold water, red and blue food dye, and an index card larger enough to cover the opening of the glasses



Fill two identical water glasses to the brim: one with hot water, the other with cold water. Put a few drops of blue dye in the cold water, a few drops of red dye in the hot water. Place the index card over the mouth of the cold water and invert the glass over the glass of hot water. Line up the openings of both glasses, and slowly remove the card.


Troubleshooting: Always invert the cold glass over the hot glass using an index card to hold the cold water in until you’ve aligned both glasses. You can also substitute soda bottles for water glasses and slide a washer between the two bottles to decrease the flow rate between the bottles so the effect lasts longer.


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Soda Can Trick

Monday May 31, 2010

When air moves, the air pressure decreases. This creates a lower air pressure pocket right between the cans relative to the surrounding air. Because higher pressure pushes, the cans clink together. Just remember – whenever there’s a difference in pressure, the higher pressure pushes.


You will need about 25 straws and two empty soda cans or other lightweight containers


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Lay a row of straws parallel to each other on a smooth tabletop. Place two empty soda cans on the straws about an inch apart. Lower your nose to the cans and blow hard through the space between the two cans.


Clink! They should roll toward each other and touch!


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Going Further with Advanced Chemistry

Monday May 31, 2010

This experiment is for advanced students.


One of my best teaching tools for science developed from a brain freeze one afternoon in class. I went to the board to draw the chlorophyll wheel and drew a complete blank.


“Let’s say I forgot how to draw the wheel.” I turned to the class, marker in hand, and scanned the room. Puzzled faces, the blank faces I expected, but, what was that? A few smiles scattered about the room.


As I pulled out and some volunteered info, we got into that wheel. They also found that it was easier to know what to do next than to have me tell them to find it in their book and be prepared…I was coming back to them. Students frantically finding the wheel in their biology books so they were armed when I came to them.


It was a great experience, and my lectures were a lot more fun and interactive from then on.


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Next, I started designing labs that way. Pre-reading was suggested, but they never read for homework…everybody knows that. But they soon found out why they should start reading ahead.


They came in for their lab.


There were a lot of lab supplies out on the counter. I had put all the supplies they would need on the counter. In addition, I put an equal number of supplies out that had nothing to do with the experiment. A problem was written at the top of the board such as, “We need to extract chlorophyll from the leaves on the counter.” And that was it. No lab book, they were on their own.


I gave a short lecture to bait their brains into remembering something and turned them loose. It took a couple of weeks, but I gained so much with them. Many more were reading at home to prepare for the lab, because they didn’t want to sit around trying to figure things out from scratch. They already had an idea on how to do the lab when they came on lab day. If they did not finish in the class time allotted, it was too bad. They could make up the lab later, but most just took the bad grade.


Many more students were motivated beyond my wildest expectations. Many students that were working hard to stay on the bottom started to feel a little peer pressure to help out. Students enjoyed the discovery…..they enjoyed the labs. No more cookie cutter labs for us.


Perhaps some labs in your curriculum could be designed to work this way as a way to provide more advanced learning in the sciences?



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Air Takes Space

Monday May 31, 2010

You’re about to play with one of the first methods of underwater breathing developed for scuba divers hundreds of years ago.! Back then, scientists would invert a very large clear, bell-shaped jar over a diver standing on a platform, then lower the whole thing into the water. Everyone thought this was a great idea, until the diver ran out of breathable air…


Materials: 12″ flexible tubing, two clear plastic cups, bathtub


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Part I: Fill the tub and climb in. Plunge one cup underwater so it fills completely with water. While the cup is underwater, point its mouth downward. Insert one end of the tubing into the cup and blow hard into the other end. The water is forced out of the cup!


Part II: While still in the tub, invert one cup (mouth downwards) and plunge it into the tub so that air gets trapped inside the cup. Place the second cup in the water so it fills with water. Invert the water-filled cup while underwater and position it above the first cup so when you tilt the first cup to release the air bubbles, they get trapped inside the second cup. Here you see that air takes space, because in both variations of this experiment the air forced the water out of the cups.


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Advanced Alternative Energy Exercises

Saturday May 1, 2010

Let’s see how much you’ve picked up with these experiments and the reading – answer as best as you can. (No peeking at the answers until you’re done!) Just relax and see what jumps to mind when you read the question. You can also print these out and jot down your answers in your science notebook.


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  1. What are three different sources of alternative energy?
  2. What’s the difference between alternative and renewable energy?
  3. What is power a measure of?
  4. What is energy?
  5. How does a solar cell work?
  6. Where does the power from a crystal radio come from?
  7. How does a wind turbine create electricity?
  8. Is a motor and generator the same thing?
  9. Does the water molecule give energy when you split it apart?
  10. Would you get more energy from splitting an atom or a proton?
  11. How can a car be powered by only sunlight and water?

Need answers?

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Answers to Advanced Alternative Energy Exercises

Saturday May 1, 2010

Let’s see how you did! If you didn’t get a few of these, don’t let it stress you out – it just means you need to play with more experiments in this area. We’re all works in progress, and we have our entire lifetime to puzzle together the mysteries of the universe!


Here’s printer-friendly versions of the exercises and answers for you to print out: Simply click here for printable questions and answers.


Answers:
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  1. Solar cells, wind turbine, hydro (water) power plants, fuel cells.
  2. Renewable energy is the energy created from natural sources, like sunlight, water, wind, and temperature differences (geothermal).
  3. Power measures how quickly work can be done.
  4. Energy is the ability to do work. Work is moving something against a force over a distance.
  5. A solar cell converts sunlight straight into electricity by using a special material that allows electrons to be knocked out of their shells when hit by a photon. The free electrons are directed into flow of DV current.
  6. The source of power comes directly from the radio waves themselves.
  7. Wind turbines spin big coils of wire around very powerful magnets when their propellers (which is attached to the motor shaft) rotate.
  8. Yes, they are the same object, but it’s how you use them that makes them different.  A motor uses electricity (applied to the terminals) to rotate the shaft, and a generator rotates the shaft to create electricity at the terminals. If you spin the shaft of a motor with your fingers, you can measure a voltage at the terminals.
  9. No. A water molecule requires energy to split it apart (endothermic reaction). When the opposite occurs – hydrogen and oxygen combine, the reaction is exothermic (gives off energy).
  10. Much more energy is released from splitting a proton than an atom.  The forces that hold together a proton are much greater than the furthers that bind an atom.
  11. When you combine oxygen and hydrogen together, it makes water and a puff of energy. That’s what a fuel cell does. Most fuel cells are reversible, meaning that you can fill their tank with water and leave them out (with their solar panel pointed toward the sun), and the solar cell will split apart the water molecule and store the gases in separate tanks.  When you’re ready to drive your car, the fuel cell switches so it now combines the gases to create electricity to turn the motor (which turn the wheels of the car).

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Solar Cookies

Saturday May 1, 2010

Can you use the power of the sun without using solar cells? You bet! We’re going to focus the incoming light down into a heat-absorbing box that will actually cook your food for you.


Remember from Unit 9 how we learned about photons (packets of light)?  Sunlight at the Earth’s surface is mostly in the visible and near-infrared (IR) part of the spectrum, with a small part in the near-ultraviolet (UV). The UV light has more energy than the IR, although it’s the IR that you feel as heat.


We’re going to use both to bake cookies in our homemade solar oven. There are two different designs – one uses a pizza box and the other is more like a light funnel. Which one works best for you?


  • Two large sheets of poster board (black is best)
  • Aluminum foil
  • Plastic wrap
  • Black construction paper
  • Cardboard box
  • Pizza box (clean!)
  • Tape & scissors
  • Reusable plastic baggies
  • Cookie dough (your favorite)

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Download Student Worksheet & Exercises


How does that work? Your solar cooker does a few different things. First, it concentrates the sunlight into a smaller space using aluminum foil. This makes the energy from the sun more potent. If you used mirrors, it would work even better!


You’re also converting light into heat by using the black construction paper. If you’ve ever gotten into car with dark seats, you know that those seats can get HOT on summer days! The black color absorbs most of the sunlight and transforms it into heat (which boosts the efficiency of your solar oven).


By strapping on a plastic sheet over the top of the pizza-box cooker, you’re preventing the heat from escaping and cooling the oven off. Keeping the cover clear allows sunlight to enter and the heat to stay in. (Remember the black stuff converted your light into heat?) If you live in an area that’s cold or windy, you’ll find this part essential to cooking with your oven!


Here’s another type of solar cooker that uses a cone design to focus the energy straight to your cookies!



Exercises Answer the questions below:


  1. Name the type of heat energy that the sun provides:
    1. Convection
    2. Conduction
    3. Radiation
    4. Invection
  2. What are some ways that the sun’s energy can be directly harnessed?
  3. Name three of the different parts of the electromagnetic spectrum:

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Solar Boat

Saturday May 1, 2010

expansionpacks_clip_image004_0000Does it really matter what angle the solar cell makes with the incoming sunlight? If so, does it matter much? When the sun moves across the sky, solar cells on a house receive different amounts of sunlight. You’re going to find out exactly how much this varies by building your own solar boat.


We’re going to use solar cells and the basic ideas from Unit 10 (Electricity & Robotics) to build a solar-powered race car.  You’ll need to find these items below.  Note – if you have trouble locating parts, check the shopping list for information on how to order it straight from us.


  • Solar motor
  • Solar cell
  • Foam block (about 6” long)
  • Alligator clip leads
  • Propeller (you can rip one off an old small personal fan or old toy, or find them at hobby stores)

Here’s what you do:


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Download Student Worksheet & Exercises


1. Attach the wires of the solar cell to the motor (one to each motor terminal).


2. Attach the propeller to your motor. If the shaft won’t fit, drill out the center hole. If the hole is too large, use a tiny dab of hot glue on the shaft tip to secure the propeller into place.


3. Stand out in the sun. How do you need to hold your solar cell to make the propellers pin the fastest?


4. Position the motor on a block of foam so that the propeller hangs off the edge and is free to rotate. Hot glue the motor into place, being careful not to get any hot glue near any vents in your motor.


5. Hot glue your solar cell to the foam block. You might want to check the final position in sunlight before attaching it.


6. Optional: Wire up a simple switch (from Unit 10) using paperclips and brass fasteners so you can easily turn your power on and off.


Going further: Using the same solar cell, you can also build a Wind Turbine and a Solar Car.


Exercises Answer the questions below:


  1. What kind of electricity comes from a battery and photovoltaic cell?
    1. Nuclear
    2. Voltaic
    3. Electrochemical
    4. Ionized
  2. Electricity is another name for the free flow of:
    1. Protons
    2. Quarks
    3. Electrodes
    4. Electrons
  3. True or false: Ions are attracted to the same charge.
    1. True
    2. False
  4. Do solar panels work in cloudy climates?
    1. Yes
    2. No

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Solar Car

Saturday May 1, 2010

solarboatSolar energy (power) refers to collecting this energy and storing it for another use, like driving a car. The sun blasts 174 x 1015 watts (which is 174,000,000,000,000,000 watts) of energy through radiation to the earth, but only 70% of that amount actually makes it to the surface. And since the surface of the earth is mostly water, both in ocean and cloud form, only a small fraction of the total amount makes it to land.


A solar cell converts sunlight straight into electricity. Most satellites are powered by large solar panel arrays in space, as sunlight is cheap and readily available out there. While solar cells seem ‘new’ and modern today, the first ones were created in the 1880s, but were a mere 1% efficient. (Today, they get as high as 35%.) A solar cell’s efficiency is a measure of how much sunlight the cell converts into electrical energy.


We’re going to use solar cells and the basic ideas from Unit 10 (Electricity & Robotics) to build a solar-powered race car.  You’ll need to find these items below.  Note – if you have trouble locating parts, check the shopping list for information on how to order it straight from us.


  • Solar cell
  • Solar motor
  • Foam block (about 6” long)
  • Alligator clip leads
  • 2 straws (optional)
  • 2 wooden skewers (optional)
  • 4 milk jug lids or film can tops
  • Set of gears, one of which fits onto your motor shaft (most solar motor kits come with a set), or rip a set out of an old toy

Here’s what you do:


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Download Student Worksheet & Exercises


How does a solar cell work? Solar cells are usually made of silicon. Sunlight is made of packets of energy called photons (we covered this in Unit 9). When photons hit the silicon, one of three things can happen: the photons can pass straight through the silicon if they have a low enough energy; they can get reflected off the surface; or (and this is the fun part) they get absorbed and the electrons in the silicon get knocked out of their shell.


Once knocked out of orbit, the free electrons start flowing through the silicon to create electricity. The solar cells are structured is such a way as to keep the electricity flowing only in one direction. The electron flow created is DC current (refer to Unit 10).


The solar cells you can buy from stores require huge amounts of energy in creating the solar cell, which is the primary downside. You need high temperatures, big vacuum pumps, and lots of people to make a set of solar cells. However, if we focus just on the physics of the solar cell, then we can easily create our own solar battery and other solar cell projects using household items. While these cells won’t look as spiffy as the ones from the store, they still produce electricity from sunlight.


Using the same solar cell, you can also build a Wind Turbine and a Solar Boat.


Exercises Answer the questions below:


  1. Most solar cells are made of what material?
    1. Hydrogen
    2. Aluminum
    3. Silicon
    4. Titanium
  2. Name one benefit of solar cells and one drawback of using them for electricity.
    1. Benefit:
    2. Drawback:
  3. Electrical current begins flowing when:
    1. Sunlight hits an atom
    2. Electrons are knocked out of orbiting atoms
    3. Protons get charged
    4. An atom’s nucleus splits

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Wind Turbine

Saturday May 1, 2010

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Believe it or not, most of the electricity you use comes from moving magnets around coils of wire! Wind turbines spin big coils of wire around very powerful magnets (or very powerful magnets around big coils of wire) by capturing the flow.


Here’s how it works: when a propeller is placed in a moving fluid (like the water from your sink or wind from your hair dryer), the propeller turns. If you attach the propeller to a motor shaft, the motor will rotate, which has coils of wire and magnets inside. The faster the shaft turns, the more the magnets create an electrical current.


The electricity to power your computer, your lights, your air conditioning, your radio or whatever, comes from spinning magnets or wires! Refer to Unit 11 for more detail about how moving magnets create electricity.


We’re going to build a wind turbine that will actually give you different amounts of electricity depending on which way your propeller is facing. Ready?


You’ll need to find these items below.  Note – if you have trouble locating parts, check the shopping list for information on how to order it straight from us.


  • A digital Multimeter
  • Alligator clip leads
  • 1.5-3V DC Motor
  • 9-18VDC Motor
  • Bi-polar LED
  • Foam block (about 6” long)
  • Propeller from old toy or cheap fan, or balsa wood airplane

Here’s what you do:


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Download Student Worksheet & Exercises


Using the same solar cell, you can also build a Solar Car and a Solar Boat.


Exercises


  1. True or false: Electricity in a wind turbine is created by magnets in the turbine:
    1. True
    2. False
  2. What is one advantage of using wind for electricity?
  3.  What might be one problem with constructing wind farms to meet all our energy needs?

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Marshmallow Roaster

Saturday May 1, 2010

Do you like marshmallows cooked over a campfire? What if you don’t have a campfire, though? We’ll solve that problem by building our own food roaster – you can roast hot dogs, marshmallows, anything you want. And it’s battery-free, as this device is powered by the sun.


NOTE: This roaster is powerful enough to start fires! Use with adult supervision and a fire extinguisher handy.


If you’re roasting marshmallows, remember that they are white – the most reflective color you can get.  If you coat your marshmallows with something darker (chocolate, perhaps?), your marshmallow will absorb the incoming light instead of reflecting it.


Here’s what you need to get:


  • 7×10” page magnifier (Fresnel lens)
  • Cardboard box, about a 10” cube
  • Aluminum foil
  • Hot glue, razor, scissors, tape
  • Wooden skewers (BBQ-style)
  • Chocolate, marshmallows, & graham crackers

Here’s what you do:



Download Student Worksheet & Exercises


How does it do that? The Fresnel lens is a lot like a magnifying glass.  In Unit 9, we learned how convex lenses are thicker in the middle (you can feel it with your fingers).  A Fresnel lens (first used in the 1800s to focus the beam in a lighthouse) has lots of ridges you can feel with your fingers.  It’s basically a series of magnifying lenses stacked together in rings (like in a tree trunk) to magnify an image.


The best thing about Fresnel lenses is that they are lightweight, so they can be very large (which is why light houses used these designs). Fresnel lenses curve to keep the focus at the same point, no matter close your light source is.


The Fresnel lens in this project is focusing the incoming sunlight much more powerfully than a regular hand held magnifier. But focusing the light is only part of the story with your roaster.  The other part is how your food cooks as the light hits it.  If your food is light-colored, it’s going to cook slower than darker (or charred) food. Notice how the burnt spots on your food heat up more quickly!


Scientifically Dissecting a Marshmallow

Plants take in energy (from the sun), water, and carbon dioxide (which is carbon and oxygen) and create sugar, giving off the oxygen. In other words: carbon + water + energy = sugar


  1. In this experiment, we will reverse this equation, by roasting a marshmallow, which is mostly sugar.
  2. When you roast your marshmallow, first notice the black color. This is the carbon.
  3. Next notice the heat and light given off. These are two forms of energy.
  4. Finally, put the roasting marshmallow if a mason jar. Notice that condensation forms on the sides. This is the water.

So, by roasting the marshmallow, we showed: sugar = carbon + water + energy!


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Steamboats

Saturday May 1, 2010

In 1920’s, these were a big hit. They were originally called “Putt Putt Steam Boats”, and were fascinating toys for adults and kids alike. We’ll be making our own version that will chug along for hours. This is a classic demonstration for learning about heat, energy, and how to get your kids to take a bath.



Here’s what you need to build your own:


  • Copper tubing (1/8”-1/4” dia x 12” long)
  • Votive candle
  • Foam block
  • Scissors or razor (with adult help)
  • Bathtub

Here’s what you need to do:



Download Student Worksheet & Exercises


  1. Wrap the copper tubing 2-3 times around a thick marker. You want to create a ‘coil’ with the tubing. Do this slowly so you don’t kink the tubing. End with two 3” parallel tails. (This is easier if you start in the middle of the tubing and work outwards in both directions.)
  2. Stick each tail through a block of foam. Bend the wires to they run along the length of the bottom of the boat, slightly pointed upwards. (You can also use a plastic bottle cut in half.)
  3. Position a votive candle on the topside of the boat and angle the coil so it sits right where the flame will be.
  4. To start your boat, fill the bathtub with water. While your tub fills, hold the tubing in the running water and completely fill the coil with water.
  5. Have your adult helper light the candle. In a moment, you should hear the ‘putt putt’ sounds of the boat working!
  6. Troubleshooting: if your boat doesn’t work, it could be a few things:
    1. The tubing has an air bubble. In this case, suck on one of the ends like a straw to draw in more water. Heating an air bubble will not make the boat move – it needs to be completely filled with water.
    2. Your coil is not hot enough. You need the water to turn into steam, and in order for this to happen, you have to heat the coil as hot as you can. Move the coil into a better position to get heat from the flame.
    3. The exhaust pipes are angled down. You want the stem to move up and out of your pipes, not get sucked back in. Adjust the exit tubing tails so they point slightly upwards.

How Do They Work? Your steam boat uses a votive candle as a heat source to heat the water inside the copper tubing (which is your boiling chamber). When the water is heated to steam, the steam pushes out the tube at the back with a small burst of energy, which pushes the boat forward.


Since your chamber is small, you only get a short ‘puff’ of energy. After the steam zips out, it creates a low pressure where it once was inside the tube, and this draws in fresh, cool water from the tub. The candle then heats this new water until steam and POP! it goes out the back, which in turn draws in more cool water to be heated… and on it goes. The ‘clicking’ or ‘putt putt’ noise you hear is the steam shooting out the back. This is go on until you either run out of water or heat.


Bonus! Here’s a video from a member that colored the water inside the pipe so they could see when it got pushed out! Note that the boat usually runs as fast as the first video on this page. The boats here are getting warmed up, ready to go, so they only do one or two puffs before they really start up.



Exercises Answer the questions below:


  1. Name three sources of renewable or alternative energy:
  2. Why is it important to look for renewable sources of energy?
  3. What is one example of a fossil fuel?

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Solar Battery

Saturday May 1, 2010

This is the kind of energy most people think of when you mention ‘alternative energy’, and for good reason! Without the sun, none of anything you see around you could be here. Plants have known forever how to take the energy and turn it into usable stuff… so why can’t we?


The truth is that we can. While normally it takes factories the size of a city block to make a silicon solar cell, we’ll be making a copper solar cell after a quick trip to the hardware store. We’re going to modify the copper into a form that will allow it to react with sunlight the same way silicon does. The image shown here is the type of copper we’re going to make on the stovetop.


This solar cell is a real battery, and you’ll find that even in a dark room, you’ll be able to measure a tiny amount of current. However, even in bright sunlight, you’d need 80 million of these to light a regular incandescent bulb.


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You’ll need to gather these materials together:


  • ½ sq. foot of copper flashing sheet (check the scrap bin at a hardware store)
  • Alligator clip leads
  • Multimeter
  • Electric stove (not gas)
  • Large plastic 2L soda bottle
  • ¼ cup salt
  • Sandpaper & sheet metal shears

Here’s what you need to do:



Download Student Worksheet & Exercises


How does that work? Do you remember learning about the photoelectric effect in Unit 9? This cuprous oxide solar cell ejects electrons when placed in UV light – and sunlight has enough UV light to make this solar cell work. Those free electrons are now free to flow – which is exactly what we’re measuring with the volt meter.


Semiconductors are the secret to making solar cells. A semiconductor is a material that is part conductor, part insulator, meaning that electricity can flow freely and not, depending on how you structure it. There are lots of different kinds of semiconductors, including copper and silicon.


In semiconductors, there’s a gap (called the bandgap) that’s like a giant chasm between the free electrons (electrons knocked out of its shell) and bound electrons (electrons attached to an atom). Electrons can be either free or attached, but it costs a certain amount of energy to go either way (like a toll both).


When sunlight hits the semiconductor material in the solar cell, some of the electrons get enough energy to jump the gap and get knocked out of their shell to become free electrons. The free electrons zip through the material and create a low of electrons. When the sun goes down, there’s no source of energy for electrons to get knocked out of orbit, so they stay put until sunrise.


Does it really matter what angle the solar cell makes with the incoming sunlight? If so, does it matter much? When the sun moves across the sky, solar cells on a house receive different amounts of sunlight. You’re going to find out exactly how much this varies by building your own solar vehicles.


Exercises Answer the questions below:


  1. The sunlight causes the electrons to flow from the cuprous oxide because of:
    1. Photosynthesis
    2. The electromagnetic spectrum
    3. The photoelectric effect
    4. The photochemical principle
  2. What material do most solar cells use instead of copper?
  1. What part of the electromagnetic spectrum is most active in this experiment?
    1. Visible Light
    2. Ultraviolet Light
    3. Gamma Rays
    4. Microwaves
  2. When you read amps, you read:
    1. Current
    2. Voltage
    3. Power Draw
    4. Work

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Crystal Radio

Saturday May 1, 2010

xtal3This project is for advanced students. A crystal radio is among the simplest of radio receivers – there’s no battery or power source, and nearly no moving parts. The source of power comes directly from the radio waves themselves.


The crystal radio turns the radio signal directly into a signal that the human ear can detect. Your crystal radio detects in the AM band that have been traveling from stations (transmitters) thousands of miles away. After working with the electromagnetic spectrum in Unit 9 where we played with frequency and wavelengths of light, you’ll find that you’ve got all the basics for picking up AM radio stations using simple equipment from an electronics store.


The radio is made up of a tuning coil (magnet wire wrapped around a toilet paper tube), a detector (germanium diode) and crystal earphones, and an antenna wire.


One of the biggest challenges with detecting low-power radio waves is that there is no amplifier on the radio to boost the signal strength. You’ll soon figure out that you need to find the quietest spot in your house away from any transmitters (and loud noises) that might interfere with the reception when you build one of these.


One of things you’ll have is to figure out the best antenna length to produce the clearest, strongest radio signal in your crystal radio. I’m going to walk you through making three different crystal radio designs.


Materials:


  • Toilet paper tube
  • Magnet wire
  • Germanium diode: 1N34A
  • 4.7k-ohm resistor
  • Alligator clip test leads
  • 100’ stranded insulated wire (for the antenna)
  • Scrap of cardboard
  • Brass fasteners (3-4)
  • Telephone handset or get a crystal earphone

Here’s what you do:


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Download Student Worksheet & Exercises


The video below shows how to make a slightly different model that uses different parts. If you have the Science Mastery Diamond program, this is the one you have the parts for. The company, GSST sadly has gone out of business, but they gave us permission to use their project guidebook with the video that we made for their kit. Download the project guidebook here and gather your materials!


Materials:


  • 8 steel (unpainted) thumbtacks
  • Toilet paper tube
  • 70 feet of #26-30 magnet wire
  • 1 large paper clip
  • 2 4″ pieces of hook up wire
  • Germanium diode: 1N34A
  • 470 pf disc capacitor
  • 0.01 mf disc capacitor
  • Alligator clip test leads
  • 100’ stranded insulated wire (for the antenna)
  • Scrap of cardboard or wood for your project
  • Crystal earphone

 



Exercises


  1. What are radio waves?
  2. Name some of the parts needed for any radio that we also used in this radio.
  3. What serves as the tuning coil for the crystal radio?
  4. Why do you need a ground for the radio?

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BEAM Robots

Saturday May 1, 2010

This project is for advanced students.This is one of the coolest applications of renewable energy to come about in recent years. BEAM stands for Biology, Electronics, Aesthetics, and Mechanics. It basically refers to a class of robots that instead of having complicated brains, rely on nervous-system type of sensors to interact with their world.


Some BEAM robots skitter, dance, flash, jump, roll, or walk, and most are solar powered. The result is a fast responding robot made of old cell phone parts that can fit inside your hand. We’ll be making a few different types so you can get a good handle on this type of programming-free, battery-free robotics.


Most BEAM robots use the same solar ‘engine’. The solar cell will convert sunlight into electricity, which will then be stored in our capacitors (think ‘electricity tanks’) until a certain threshold is reached… when the tanks are full, the robot begins to move. This means that you can leave them out all day, and they will sit and collect energy, then turn on by themselves until they run out of juice, then turn off, sit and recharge until they have enough energy to go again… and off they go!


Let’s walk through how to make a BEAM robot. Once you’ve got the hang of it, make a second solar engine from the rest of your parts and add any kind of body you want!


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You’ll need to get the following materials:


Here’s what you do…


Beam Robot:


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Bristle Brush Bot

Saturday May 1, 2010

This is the simplest robot you can make… out of old parts from around the house. While this little robot doesn’t use energy from the sun or wind, we’ve placed it here with other alternative energy projects because the parts come from the trash bin.


This project is an extension of the Jigglebot robot from Unit 10.


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You’ll need to find:


  • Old toothbrush you can destroy
  • Tiny vibrator motor (you can rip one out of an old cell phone) – just make sure it’s got a weight attached to the motor shaft.
  • Small watch battery (make sure it’s around 3V to match the motor)
  • Scissors and/or razor
  • Tape and a hot glue gun
  • Optional: Paper clips for claws and feet

Here’s what you do:



What’s going on? Your BristleBot uses the toothbrush bristles as legs and an eccentric motor to shake and wobble it by tiny amounts to look like a smooth motion. The larger the weight, the more you’ll see the wobbling action. Try making one out of the head of a scrub brush or small broom!


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Stirling Engine

Saturday May 1, 2010

This project is for advanced students.This Stirling Engine project is a very advanced project that requires skill, patience, and troubleshooting persistence in order to work right.  Find yourself a seasoned Do-It-Yourself type of adult (someone who loves to fix things or tinker in the garage) before you start working on this project,  or you’ll go crazy with nit-picky things that will keep the engine from operating correctly.  This makes an excellent project for a weekend.


Developed in 1810s, this engine was widely used because it was quiet and could use almost anything as a heat source. This kind of heat engine squishes and expands air to do mechanical work. There’s a heat source (the candle) that adds energy to your system, and the result is your shaft spins (CD).


This engine converts the expansion and compression of gases into something that moves (the piston) and rotates (the crankshaft). Your car engine uses internal combustion to generate the expansion and compression cycles, whereas this heat engine has an external heat source.


This experiment is great for chemistry students learning about Charles’s Law, which is also known as the Law of Volumes, which describes how gases tend to expand when they are heated and can be mathematically written like this:



where V = volume, and T = temperature. So as temperature increases, volume also increases. In the experiment you’re about to do, you will see how heating the air causes the diaphragm to expand which turns the crank.


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Here’s what you need:


  • three soda cans
  • old inner tube from a bike wheel
  • super glue and instrant dry
  • electrical wire (3- conductor solid wire)
  • 3 old CDs
  • one balloon
  • penny
  • nylon bushing (from hardware store)
  • alcohol burner (you can build one out of soda cans or Sterno canned heat)
  • fishing line (15lb. test or similar)
  • pack of steel wool
  • drill with 1/16″ bit
  • pliers
  • scissors
  • razor
  • wire cutters
  • electrical tape
  • push pin
  • permanent marker
  • Swiss army knife (with can opener option)
  • template
  • HINT: The “circle template” mentioned at 21:57 is actually just a circle traced from the bottom of the soda can onto a sheet of paper

The Stirling heat engine is very different from the engine in your car.  When Robert Stirling invented the first Stirling engine in 1816, he thought it would be much more efficient than a gasoline or diesel engine. However, these heat engines are used only where quiet engines are required, such as in submarines or in generators for sailboats.



Download Student Worksheet & Exercises


Here’s how a Stirling engine is different from the internal-combustion engine inside your car. For example, the gases inside a Stirling engine never leave the engine because it’s an external combustion engine. This heat engine does not have exhaust valves as there are no explosions taking place, which is why Stirling engines are quieter. They use heat sources that are outside the engine, which opens up a wide range of possibilities from candles to solar energy to gasoline to the heat from your hand.


There are lots of different styles of Stirling engines. In this project, we’ll learn about the Stirling cycle and see how to build a simple heat engine out of soda cans.  The main idea behind the Stirling engine is that a certain volume of gas remains inside the engine and gets heated and cooled, causing the crankshaft to turn. The gases never leave the container (remember – no exhaust valves!), so the gas is constantly changing temperature and pressure to do useful work.  When the pressure increases, the temperature also increases. And when the temperature of the gases decreases, the pressure also goes down. (How pressure and temperature are linked together is called the “Ideal Gas Law”.)


Some Stirling engines have two pistons where one is heated by an external heat source like a candle and the other is cooled by external cooling like ice. Other displacer-type Stirling engines has one piston and a displacer. The displacer controls when the gas is heated and cooled.


In order to work, the heat engine needs a temperature difference between the top and bottom of the cylinder. Some Stirling engines are so sensitive that you can simply use the temperature difference between the air around you and the heat from your hand. Our Stirling engine uses temperature difference between the heat from a candle and ice water.


The balloon at the top of the soda can is actually the ‘power piston’ and is sealed to the can.  It bulges up as the gas expands. The displacer is the steel wool in the engine which controls the temperature of the air and allows air to move between the heated and cooled sections of the engine.


When the displacer is near the top of the cylinder, most of the gas inside the engine is heated by the heat source and gas expands (the pressure  builds inside the engine, forcing the balloon piston up). When the displacer is near the bottom of the cylinder, most of the gas inside the engine cools and contracts. (the pressure decreases and the balloon piston is allowed to contract).


Since the heat engine only makes power during the first part of the cycle, there’s only two ways to increase the power output: you can either increase the temperature of the gas (by using a hotter heat source), or by cooling the gases further by removing more heat (using something colder than ice).


Since the heat source is outside the cylinder, there’s a delay for the engine to respond to an increase or decrease in the heat or cooling source. If you use only water to cool your heat engine and suddenly pop an ice cube in the water, you’ll notice that it takes five to fifteen seconds to increase speed. The reason is because it takes time for the additional heat (or removal of heat by cooling) to make it through the cylinder walls and into the gas inside the engine. So Stirling engines can’t change the power output quickly. This would be a problem when getting on the freeway!


In recent years, scientists have looked to this engine again as a possibility, as gas and oil prices rise, and exhaust and pollutants are a concern for the environment. Since you can use nearly any heat source, it’s easy to pick one that has a low-fume output to power this engine. Scientists and engineers are working on a model that uses a Stirling engine in conjunction with an internal-combustion engine in a hybrid vehicle… maybe we’ll see these on the road someday!


Exercises


  1. What is the primary input of energy for the Stirling engine?
  2.  As Pressure increases in a gas, what happens to temperature?
    1. It increases
    2. Nothing
    3. It decreases
    4. It increases, then decreases
  3. What is the primary output of the Stirling engine?

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Fuel Cell Power

Saturday May 1, 2010

41wpr5+y2qLThis project is for advanced students. We’re going to build a car that runs entirely on sunlight and water.  Use energy from the sun, we’ll first use a solar cell to convert sunlight into electricity.


Then we’ll use that electricity to split the water molecule (H2O) into hydrogen and oxygen atoms and store them in separate tanks.


Lastly, we’ll flip the system around to allow the hydrogen and oxygen gases to mix, which will produce the power to run the car and create an exhaust product that’s just plain water.


How does that sound?
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We’re going to use solar cells and the basic ideas from Unit 10 (Electricity & Robotics) and Unit 8: Chemistry to build a fuel cell vehicle.  The fuel cell is reversible, meaning that you can use it to pull apart water molecules into atomic gases, or combine the atomic gases together to make water.


You’ll need to order the Fuel Cell Car Kit (Item# KT-FUELCCK from www.hometrainingtools.com). This kit is a bit expensive, but if you want to build a car that runs entirely from sunlight and water, this is the one you want to get.  The company that makes this particular model also sells the conversion kits for (real!) cars.


Here’s what you do:



How does that work? Molecules can also be split chemically, or by getting hit by a fast-moving particle. When you recombine the hydrogen and oxygen, energy is produced – enough to power a small car. If you guessed that this has to do with Unit 10: Electricity and Unit 8: 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.


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. We covered the basics of electrolysis in Unit 8, and now we’re going to show you how to store the energy and use it power a small car in our fuel cell project together.


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BEAM Robot: Solar Roller

Saturday May 1, 2010

Note: Brian Cox has created a BEAM Bot kit as an alternative BEAM project.

Brian's BEAM BOT is modeled after small BEAM projects where parts are soldered to each other, but such projects can be difficult to solder.

BEAM Bot uses a standard Printed Circuit Board (PCB) as the frame thus making it easier to assemble.

You can order Brian's BEAM Bot Kit here: fvresearch.com/product/beam-bot .

Click here for Brian's BEAM Bot instructional video (which can be found under Unit 25).

This project is for advanced students.This is one of the coolest applications of renewable energy to come about in recent years. BEAM stands for Biology, Electronics, Aesthetics, and Mechanics. It basically refers to a class of robots that instead of having complicated brains, rely on nervous-system type of sensors to interact with their world.

Some BEAM robots skitter, dance, flash, jump, roll, or walk, and most are solar powered. The result is a fast responding robot made of old cell phone parts that can fit inside your hand. We'll be making a few different types so you can get a good handle on this type of programming-free, battery-free robotics.

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To make this project, you'll need to get the Solar Roller kit from Solarbotics. You'll also need your soldering equipment and basic tools, like pliers, wire strippers, scissors, and electrical tape.



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BEAM Robot: Trimet

Saturday May 1, 2010

Note: Brian Cox has created a BEAM Bot kit as an alternative to the Trimet project.

Brian's BEAM BOT is modeled after small BEAM projects where parts are soldered to each other, but such projects can be difficult to solder.

BEAM Bot uses a standard Printed Circuit Board (PCB) as the frame thus making it easier to assemble.

You can order Brian's BEAM Bot Kit here: fvresearch.com/product/beam-bot .

Click here for Brian's BEAM Bot instructional video (which can be found under Unit 25).

This project is for advanced students. This is one of the coolest applications of renewable energy to come about in recent years. BEAM stands for Biology, Electronics, Aesthetics, and Mechanics. It basically refers to a class of robots that instead of having complicated brains, rely on nervous-system type of sensors to interact with their world.

Some BEAM robots skitter, dance, flash, jump, roll, or walk, and most are solar powered. The result is a fast responding robot made of old cell phone parts that can fit inside your hand. We'll be making a few different types so you can get a good handle on this type of programming-free, battery-free robotics.

You'll need to get the Trimet Kit from Solarbotics. It has everything you need except the tools for the job (soldering iron, pliers, wire strippers, razor) and paperclips.

Here's what you do:

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BEAM Robot: MiniBall

Saturday May 1, 2010

This project is for advanced students.This is one of the coolest applications of renewable energy to come about in recent years. BEAM stands for Biology, Electronics, Aesthetics, and Mechanics. It basically refers to a class of robots that instead of having complicated brains, rely on nervous-system type of sensors to interact with their world.

Some BEAM robots skitter, dance, flash, jump, roll, or walk, and most are solar powered. The result is a fast responding robot made of old cell phone parts that can fit inside your hand. We'll be making a few different types so you can get a good handle on this type of programming-free, battery-free robotics.

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You'll need to get the MiniBall Kit from Solarbotics. It has everything you need except the tools for the job (soldering iron, pliers, wire strippers, razor), paperclips, and 80mm plastic ball (the kind found at craft stores for making your own holiday ornaments).

Here's what you do:

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Lesson 2: Advanced Alternative Energy Video

Saturday May 1, 2010

What’s all the hype about “Alternative Energy”? Are there really better ways of making the same energy for less? Absolutely! One of the biggest challenges we have right now is how to extract the energy that’s already around us. For example, the amount of energy in a gallon of water could power all of the USA for a year, if we only knew how to harness it safely.


There are many different forms of energy floating around you right now: solar batteries capture the heat and light energy from the sun and store it for later use; geothermal energy uses the difference in temperature to do work; the energy from rushing winds and rivers can be used to turn a motor; and the energy inside light waves themselves can be tapped into so you can hear radio signals using a battery-free radio.


We’re going to cover all this and more, including how to get energy from the water molecule to power a vehicle AND how to build robots that use only solar power (and never need a battery recharge!) Are you ready? Then let’s start with this video:


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Electromagnets Exercises

Sunday April 4, 2010

Let’s see how much you’ve picked up with these experiments and the reading – answer as best as you can. (No peeking at the answers until you’re done!) Just relax and see what jumps to mind when you read the question. You can also print these out and jot down your answers in your science notebook.


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(Don’t be fooled by the small number of questions here… if you can answer these accurately, you’ve mastered the lesson.)


1. How does a moving magnet make electricity?
2. What’s an electromagnet?
3. How does the DC motor you built work?
4. What is a reed switch?
5. How does a magnet make sound?


Need answers?

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Magnets Exercises

Sunday April 4, 2010

Let’s see how much you’ve picked up with these experiments and the reading – answer as best as you can. (No peeking at the answers until you’re done!) Just relax and see what jumps to mind when you read the question. You can also print these out and jot down your answers in your science notebook.


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1. What happens when you break a magnet in half? Can you separate the North and South poles?
2. What causes magnetism?
3. Why does your refrigerator magnet stick to the fridge door?
4. Is aluminum magnetic, electrically conductive, or both?
5. What elements would you guess to be in a magnet? Can you name three?
6. What causes (or creates) magnetic field?
7. Name the biggest magnet you can think of.
8. Where is the magnetic south pole?
9. What happens when you heat up a magnet?
10. Why is the grape repelled by the magnet?
11. Why does the magnet go slowly down the ramp?


Need answers?

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Answers to Electromagnetism Exercises

Sunday April 4, 2010

Let’s see how you did! If you didn’t get a few of these, don’t let it stress you out – it just means you need to play with more experiments in this area. We’re all works in progress, and we have our entire lifetime to puzzle together the mysteries of the universe!


Here’s printer-friendly versions of the exercises and answers for you to print out: Simply click here for printable questions and answers.


Answers:
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1. If you moved that magnet back and forth along a wire-wrapped nail fast enough you could power a light bulb. (However, by fast enough, I mean like 1000 times a second or more!)


2. A magnet that you can turn on and off using electricity. An example is a nail wrapped in a coil of wire, powered by a battery pack.


3. The coil is magnetized (becomes an electromagnet) and is momentarily attracted to the permanent magnet and starts to align itself with it, but as it does, it breaks the connection and the coil becomes just a piece of unmagnetized wire, which continues to rotate from the previous pull (when it was magnetic). As it does, the coil energizes again, now repelling itself and pushing itself away as it tries to align itself with the magnet again, and as it does, the electricity goes off again, allowing the coil to rotate freely (and not get stuck in one position). And on it goes.


4. It’s a switch that connects (turns on) when a magnet is close by. The two small steel plates hit each other and allow electricity to flow.


5. Magnetism can create electricity and electricity can create magnetism. Sound is vibrations. To make a speaker, we need to somehow make something vibrate. The radio provides the electricity that gets pumped through the wires. The radio very quickly pumps electricity in one direction and then switches to pump it in the other direction. This movement of electrons back and forth creates a magnetic field in the coil of wire. Since the electricity keeps reversing, the magnetic field keeps reversing. Basically, the poles on the electromagnet formed by the coil go from north to south and back again. Since the poles keep reversing, the permanent magnet you have taped to the cup keeps getting attracted, then repelled, attracted, then repelled. This causes vibrations. The speaker cone (or cup, as in the speaker we’re going to make) that’s strapped to the coil and magnet acts as a sound cone. The magnet causes the sound cone to vibrate and since it’s relatively large, it causes air to vibrate. This is the sound that you hear.


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Answers to Magnets Exercises

Sunday April 4, 2010

Let’s see how you did! If you didn’t get a few of these, don’t let it stress you out – it just means you need to play with more experiments in this area. We’re all works in progress, and we have our entire lifetime to puzzle together the mysteries of the universe!


Here’s printer-friendly versions of the exercises and answers for you to print out: Simply click here for printable questions and answers.


Answers:
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1. You get two smaller magnets, each with their own north and south pole. You cannot separate the north and south pole of a manget.


2. Electrons. More accurately, a majority of electrons moving in a similar direction creates a magnetic field.


3. Electrons move on their own. They move around the nucleus and they spin. It’s the electron spin that tends to be responsible for the magnetic field in those “permanent” magnets (the magnets that maintain a magnetic field without electricity flowing).


4. Aluminum conducts electricity, but is not magnetic as detectable by the human eye (called ferromagnetic). Aluminum is technically paramagnetic (very weakly attracted to both poles of a magnet).


5. Iron, nickel, and cobalt are ferromagnetic (attracted to both poles of the magnet).


6. A magnetic field is something I can’t tell you about – it just is (like gravity). Best thing I can do is tell you that a field is an area around an electrical, magnetic or gravitational source that will create a force on another electrical, magnetic or gravitational source that comes within the reach of the field.


7. The earth. On a universe-scale, magnetars (magnetized neutron stars) are the biggest known magnets out there.


8. Off the coast of Antarctica in the ocean.


9. When you heat a magnet past the ‘Curie Temperature’, the magnet loses its magnetism. Once cooled back down, it will regain magnetism again.


10. The grape contains sugar water, which is diamagnetic (repelled by both poles).


11. The eddy currents in the metal plate created by the moving (sliding) magnet slow down the magnet and counteracts gravity.


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Galvanometers

Sunday April 4, 2010

Galvanometers are coils of wire connected to a battery. When current flows through the wire, it creates a magnetic field. Since the wire is bundled up, it multiplies this electromagnetic effect to create a simple electromagnet that you can detect with your compass.
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Here’s what you need to do:


Materials:


  • magnet wire
  • sand paper
  • scissors
  • compass
  • AA battery case
  • 2 AA batteries
  • 2 alligator clip wires


Download Student Worksheet & Exercises


1. Remove the insulation from about an inch of each end of the wire. (Use sandpaper if you’re using magnet wire.)


2. Wrap the wire at least 30-50 times around your fingers, making sure your coil is large enough to slide the compass through.


3. Connect one end of the wire to the battery case wire.


4. While looking at the compass, repeatedly tap the other end of the wire to the battery. You should see the compass react to the tapping.


5. Switch the wires from one terminal of the battery to the other. Now tap again. Do you see a difference in the way the compass moves?


You just made a simple galvanometer. “Oh boy, that’s great! Hey Bob, take a look! I just made a….a what?!?” I thought you might ask that question. A galvanometer is a device that is used to find and measure electric current. “But, it made a compass needle move…isn’t that a magnetic field, not electricity?” Ah, yes, but hold on a minute. What is electric current…moving electrons. What do moving electrons create…a magnetic field! By the galvanometer detecting a change in the magnetic field, it is actually measuring electrical current! So, now that you’ve made one let’s use it!


More experiments with your galvanometer

You will need:


  • Your handy galvanometer
  • The strongest magnet you own
  • Another 2 feet or more of wire
  • Toilet paper or paper towel tube

1. Take your new piece of wire and remove about an inch of insulation from both ends of the wire.


2. Wrap this wire tightly and carefully around the end of the paper towel tube. Do as many wraps as you can while still leaving about 4 inches of wire on both sides of the coil. You may want to put a piece of tape on the coil to keep it from unwinding. Pull the coil from the paper towel tube, keeping the coil tightly wrapped.


3. Hook up your new coil with your galvanometer. One wire of the coil should be connected to one wire of the galvanometer and the other wire should be connected to the other end of the galvanometer.


4. Now move your magnet in and out of the the coil. Can you see the compass move? Does a stronger or weaker magnet make the compass move more? Does it matter how fast you move the magnet in and out of the coil?


Taa Daa!!! Ladies and gentlemen you just made electricity!!!!! You also just recreated one of the most important scientific discoveries of all time. One story about this discovery, goes like this:


A science teacher doing a demonstration for his students (can you see why I like this story) noticed that as he moved a magnet, he caused one of his instruments to register the flow of electricity. He experimented a bit further with this and noticed that a moving magnetic field can actually create electrical current. Thus tying the magnetism and the electricity together. Before that, they were seen as two completely different phenomena!


Now we know, that you can’t have an electric field without a magnetic field. You also cannot have a moving magnetic field, without causing electricity in objects that electrons can move in (like wires). Moving electrons create a magnetic field and moving magnetic fields can create electric currents.


“So, if I just made electricity, can I power a light bulb by moving a magnet around?” Yes, if you moved that magnet back and forth fast enough you could power a light bulb. However, by fast enough, I mean like 1000 times a second or more! If you had a stronger magnet, or many more coils in your wire, then you could make a greater amount of electricity each time you moved the magnet through the wire.


Believe it or not, most of the electricity you use comes from moving magnets around coils of wire! Electrical power plants either spin HUGE coils of wire around very powerful magnets or they spin very powerful magnets around HUGE coils of wire. The electricity to power your computer, your lights, your air conditioning, your radio or whatever, comes from spinning magnets or wires!


“But what about all those nuclear and coal power plants I hear about all the time?” Good question. Do you know what that nuclear and coal stuff does? It gets really hot. When it gets really hot, it boils water. When it boils water, it makes steam and do you know what the steam does? It causes giant wheels to turn. Guess what’s on those giant wheels. That’s right, a huge coil of wire or very powerful magnets! Coal and nuclear energy basically do little more than boil water. With the exception of solar energy almost all electrical production comes from something huge spinning really fast!


Exercises


  1. Why didn’t the coil of wire work when it wasn’t hooked up to a battery? What does the battery do to the coil of wire?
  2. How does a moving magnet make electricity?
  3. What makes the compass needle deflect in the second coil?
  4. Does a stronger or weaker magnet make the compass move more?
  5. Does it matter how fast you move the magnet in and out of the coil?

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Eddy Currents and Magnetic Brakes

Sunday April 4, 2010

Eddy currents defy gravity and let you float a magnet in midair. Think of eddy currents as brakes for magnets. Roller coasters use them to slow down fast-moving cars on tracks and in free-fall elevator-type rides.


Here’s what you need to do this activity:


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Find a thick piece of metal, like copper or aluminum to work with your neodymium magnets.


Materials:


  • aluminum block (the thicker the better, although you can try a cookie sheet)
  • neodymium disc magnets

When you have your parts, you can watch the video:




What’s going on? Here’s the basic idea: when a magnet moves near an object that conducts electricity (usually metal), it creates electric currents called eddy currents which start to flow in the conductor. These eddy currents create magnetic fields (electricity causes magnetism, remember?) in the opposite direction of the moving magnet, slowing an object down so it appears to float.


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