Question

A student studying static electricity conducts an experiment to examine how charged objects interact. She rubs a plastic comb with wool and places it on a watch glass. She then rubs a second plastic comb with wool and slowly brings it near one end of the comb.

What is the charge on the first comb?

A) Negative
B) Positive
C) Neutral

Answer 1

Upon rubbing a plastic comb with wool, the comb becomes negatively charged due to the transfer of electrons from the wool to the plastic, giving the first comb a negative charge.

Step-by-step explanation:

When the student conducts an experiment with static electricity and rubs two plastic combs with wool, she is engaging in a process known as triboelectric charging. This involves transferring electrons between two materials, causing one to gain electrons and become negatively charged, and the other to lose electrons and become positively charged. According to the principles of static electricity, similar materials such as plastic, when rubbed with wool, will typically become negatively charged. Therefore, when the student rubs the plastic comb with wool and brings a similarly charged second comb close, the two combs will repel each other because they are both negatively charged.

The charge on the first comb after being rubbed with wool is negative. This is because the plastic has a greater affinity for electrons than the wool, causing it to gain electrons and become negatively charged. The second comb would also be negatively charged for the same reason, leading to a repulsive force between the two combs if brought close together.