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Building an Electroscope

Ages: 06 - 10
Materials: Large glass jar, stranded wire, aluminum foil, plastic lid.
Time Required: 30 - 60 minutes

getting started

1. Cut two strips of unwrinkled aluminum foil, each the size of the one shown below.

Step 1   

2. Put them on a piece of thick cardboard and use a sharp object to make a hole near one end of each strip.

Step 2   

3. Also make a small hole in the center of the plastic lid.

Step 3   

4. Cut a piece of stranded wire to about the same lengths as the one in this drawing. Strip the insulation from each end and twist all the strands at one end. At the other end, divide the strands into two groups. Twist each group separately and form two hooks, as shown.

Step 4   

5. Thread the twisted end through the hole in the plastic lid, and pull the wire through so it fits snugly in the lid.

Step 5   

6. Form a loop at the top with the twisted end.

Step 6   

7. Hang the foil leaves on the two hooks of the wire. Be sure that the leaves hang straight, are close together, and move freely. Enlarge the holes if necessary.

Step 7   

8. Put the lid assembly on the jar and tape it in place.

Step 8   

9. Now let's see if the electroscope works. Comb your hair briskly, and bring the charged comb near the loop. Watch the leaves. If they swing out, the scope works. If nothing happens, check to make sure the leaves are hanging straight and are free to move on the wire. Try again.

Step 9   

10. OK, the scope appears able to detect charge. But can it hold a charge? Find out by recharging your comb, only this time pass it gently along and against the loop. If the leaves stay out when you remove the comb, you're in business.

Step 10   

11. To discharge your electroscope, simply touch the loop with your finger. The leaves should drop immediately.

Step 11   

So your electroscope works. But do you know WHY? This is what science is all about, trying to make sense out of what we see around us. That's why scientists develop theories, or models to help explain what they observe. Theories may have to be changed if new facts are discovered, but that's also part of science.

Remember to play it safe around electricity. Use caution and wear safety glasses and other appropriate dress when building and performing experiments.