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…

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.

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:

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.

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!)

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:

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!

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:

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:

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!

Click here to go to next lesson on Alien Detector.

This 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)

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.