Rubber rods charged by rubbing with cat fur repel each other. Glass rods charged by rubbing with silk repel each other. A rubber rod and a glass rod charged respectively as above attract each other. A possible explanation is that
A) Any two rubber rods charged this way have opposite charges on them.
B) Any two glass rods charged this way have opposite charges on them.
C) A rubber rod and a glass rod charged this way have opposite charges on them.
D) All rubber rods always have an excess of positive charge on them.
E) All glass rods always have an excess of negative charge on them.

Question

Quizplus · Accepted Answer

Rubber and glass have different electron affinities, so when rubbed with different materials they acquire different charges. Rubber becomes negatively charged and glass positively charged. Since opposites attract, the rubber and glass rod attract each other.

Rubber Rods Charged by Rubbing with Cat Fur Repel Each