If you charge a pocket comb by rubbing it with a silk scarf, how can you determine if the comb is positively or negatively charged?

Explanation:

It is known that like charges tend to repel each other whereas unlike charges tend to attract each other. This means that two positive charges when come closer to each other will repel each other and if a negative charge comes in contact with a positive charge then both of them will attract each other.

Therefore, when you charge a pocket comb by rubbing it with a silk scarf then the scarf will obtain a certain charge. But as we place this silk scarf closer to the comb then if the scarf gets attracted towards the comb then it means opposite charges are present on both comb and the scarf.

But if the scarf and comb repel each other then it means opposite charges are present on them.

work: w = fd (given)

work done by chet   =50*1 = 50 j

work done by mika =40*2 = 80 j

work done by sara =30*1.5 = 45 j

work done by bill =60*0.5 = 30 j

students in order from the greatest amount of work done to the least is mika> chet> sara> bill

hence option (b) is correct.

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