Physics Demonstrations at Cal Poly Pomona
Demo Index:
Pira Index:
Title:
Description:
Shows that like charges repel.
Equipment:
1. Two empty soda cans on strings & two coated ping pong balls on strings
2. Lab stand w/PVC cover for insulation
3. Short rod w/ 90° clamp
4. 90° clamp w/ short piece of rubber hose
5. PVC rod & paper towel
6. Electrophorus (Acrylic plate (clear) & aluminum disk w/ cup for handle)
The PVC on the rod can be charged using the paper towel to reduce the cans attraction to the support rod.
Procedure:
1. The two cans and two ping-pong balls hang from the horizontal rod.
2. Charge the electrophorus w/ the paper towel: Rub paper towel across acrylic to charge plate positively. Set charge disk on plate, touch metal disk with your finger. Lift disk, now negatively charged, by handle. Touch disk to cans.
3. Charge the PVC rod w/ paper towel and bring it near the cans. Watch the cans separate.
4. The experiment can be repeated with the ping-pong balls.
