Attraction and repulsion of charged styrofoam balls.

Attraction and repulsion of charged styrofoam balls. Two Styrofoam balls are balanced on a needle-point support. Cat fur rubbed on one ball will impart a negative charge. Saran Wrap rubbed on the other ball will impart a positive charge. Two other Styrofoam balls on sticks can be charged positively or negatively. A ball-on-stick charged negatively will repulse a negatively charged ball on the needle-point support, causing the support to rotate away. A negative ball-on-stick will attract the positively charged ball on the needle-point support, rotating the assembly toward it. Colored tape on rods represents charge: black = negative, red = positive: Do not mix them up!