University of Virginia
Physics Department

## Neon Bulbs and Motion of Charge

A Physical Science Activity

### Student Activity

Materials

• Small neon light bulb
• Several drinking straws
• Scissors
• Glass or plastic rod
• Wool, silk or fur
• Styrofoam cup

Procedure to make light shield:

Make a light shield for the neon bulb. It will be easier to see what is happening inside the bulb with a white backing made out of straw. Note: The bulb can also be taped to a white or a black piece of paper.

1. Cut about a four cm length of straw. Cut away half of it for about one cm.
2. Cut slits about a half cm up the straw.
3. Bend the leads of the neon bulb out at right angles and slide the neon bulb into the cut away part of the straw, leads first, so that you can see both electrodes of the bulb and the leads stick out from the slits in the straw.

Procedure:

Investigating charge transfer with the neon bulb.

To use the neon bulb, hold one lead in your hand and touch the other lead to a charged object while watching the electrodes. Try the following tests: (NEVER STICK A WIRE INTO AN 110-V ELECTRICAL SOCKET!):

• Charge a Styrofoam cup by charging the glass rod and then discharging it on the cup. The rod should be charged by rubbing with fur or silk and then discharged by touching the cup. Don't let anything else touch the cup besides the table it rests on. Touching something will discharge the stored charge on the cup. Repeat this process four or five times. Then touch one lead to the cup while holding the other lead. Note which electrode flashes and write it down.
• Rub part of a balloon with wool. Touch one lead to the charged portion of the balloon while holding the other lead. Note: This will only work on extremely dry days when enough charge can be built up on the balloon. Note which electrode flashes and write it down.
• Try rubbing your shoes across carpet and touching one lead of the bulb on a neutral object while holding the other lead. Note: Again this will only work on extremely dry days allowing sufficient charge to build up. Note which electrode flashes and write it down.

Data Sheet

Questions:

1. Why does the bulb light in each of those tests?

2. For each test, tell which object, your hand or the charged object, was losing electrons. You should be able to determine this by observing which electrode flashed.

3. When you rub your feet on the floor what is happening?