# Teacher Activities

A partial listing of the teacher activities is contained here.

### Testing for Conductors and Insulators

Materials: 1.5 V battery,1.5 V flashlight,(optional: bulb and battery holders), wire (about 12 inches), various objects that you can find (you will be testing these for conductivity; whether they can pass current).

Attach one end of the bulb to the battery and connect wires to the other ends of the bulb and battery. These will be your test wires. Once you have a collection of materials that you think may be conductors and insulators, you are ready to start testing. Place the object in question between your test wires - if the bulb lights, the circuit was completed and the material that you are testing is a conductor. If the bulb does not light, then the circuit is not complete and the material is an insulator.

### Charging by Friction

1. Rub a Styrofoam cup or a plastic ruler with the cat fur. Bring the cup near to the back of your neck or the hairs on your arm. What do feel?

2. Now, bring the cup near to some bits of paper (small paper punchings) on the table. What happens? How far away can you be and still have something happen?

3. Put a mixture of salt and pepper on a white piece of paper. Hold the cup above the salt and pepper. Can you separate the salt from the pepper? Why?

4. Hang another foam cup from the ceiling so that it hangs about three feet from the floor. Charge the cup hanging from the ceiling with the fur and bring the first cup near it. What happens to the hanging cup? Does distance have an effect?

5. You could hang several charged cups from the ceiling and watch what happens as you bring them close to each other.

6. Hang a charged suspended cup from the ceiling so that it can swing just above the table. Have one or more cups taped to the surface of the table and see how the cups interact when the hanging cup is pulled to the side and released at different distances. How does the distance the cup is pulled back affect the interaction? Place a couple pennies on the swinging cup. How does the weight affect the interaction? (This experiment is similar to atomic scattering!)

### Electroscopes

An electroscope is any device that is used to detect the presence of electric forces.

"Pith-ball" electroscope:

1. Apply glue to a small strip of aluminum foil and wrap a single layer around a straw. Cut the foiled straw into one centimeter long pieces and place a piece of string (10 cm long) between the straw and the foil before the glue dries. You now have a pith-balls!

2. Tape a straw onto an upside down foam cup with the flexible end of the straw facing up. Bend the straw so that the short end is horizontal and about 7 cm above the cup. Cut several slits into the straw and hang a pith-ball by slipping the string into the slit of the straw. You now have an electroscope!

3. Rub another foam cup with the fur and bring it near the pith-ball. What happens to the pith-ball? Carefully touch the cup to the pith ball. What happens?

4. You may want to hang several pith-balls from the straw and repeat part 3. What happens if you touch one pith ball and not the other?

### Glowing Fluorescent Bulb Through Static Electricity

You will need to turn off the lights for this experiment. The last experiment with the neon bulb showed current electricity and its relation to static electricity. This experiment is expounding on that idea.

1. Hold the fluorescent bulb (get it from the instructor) upright with one end on the floor. Rub the bulb vigorously with the cat fur being careful not to break the bulb. What do you see?

You should see the bulb glow where you just rubbed. The gas inside the bulb glows when it feels a potential difference along the tube. Your rubbing produces static charge, which as you rub the tube in different places produces a potential difference along the tube.

### Penny and Dime Battery

Materials:
Ten Pennies, Ten Dimes, Glass of Water, Vinegar, Paper Towel or heavy paper, Scrub Brush, soap and water,

Procedure:
Scrub the pennies and dimes with the brush, soap and water until they are no longer dirty. Add a tablespoon of vinegar to the glass of water. Cut the paper towel or heavy paper into about 1 inch squares. Put these into the vinegar water and let them get soaked through. Start stacking your pennies and dimes - start with a penny first, then a piece of paper, then a dime, then paper and so on. Make sure that you end with a dime if you start with a penny - the top coin and the bottom coin must be different. Connect the wires to the top and the bottom of the stack and measure the voltage that the stack has generated. Now vary the height of the stack, making sure to always keep opposite coins on top and bottom. Does the number of coins in the stack make a difference in the voltage that they produce? Why do the coins have to be cleaned? Where does the electricity come from? Why do we soak the paper towels in the vinegar water?

### A Green Potato

Cut a potato in half and make two slits in the face with a knife. Clean two pennies and insert them half way into the slits. Attach leads to the pennies, and attach these to opposite terminals of a battery. After 30 minutes to an hour, look at the potato. You will notice a greenish color around the penny connected to the positive terminal of the battery. This is copper oxide - the same greenish material that coats copper statues (such as the Statue of Liberty) when they are exposed to weather. We have ionized the copper on the penny attached to the positive terminal of the battery, giving the copper atoms a positive charge and changing them chemically. They try to move away from the positive terminal toward the negative terminal. We can see this as the green that has migrated away from the penny into the potato!