Question

an initially neutral plastic pipe is rubbed with an initially neutral cloth. Both objects are now charged, and it is shown that the pipe is negatively charged. Explain both answers.

a) Describe the charge state of the cloth.

b) Would the total charge of the pipe and the cloth (added together) be positive, negative or zero?

Answer 1

a)

It is given that both the plastic pipe and cloth are neutral. This means the number of positive and negative charge in both the substances are same. Thus, the net charge is zero.

As both the substances are rubbed each other, it is found that the plastic pipe is negatively charge. This means some negative charges are transferred from the cloth to the pipe. It also suggest that the pipe is excess of negative charge transferred from the cloth due to the conservation of charge. Thus, the cloth will have deficient negative charge or excess positive charge. The net result is that the cloth is positive charge.

Therefore, the cloth will have positive charge.

b)

It is known that the charges are transferred from pipe to cloth or cloth to pipe. But still the number of positive and negative charges together in the pipe and cloth will remain the same. Thus, the net total charge in the pipe and cloth will be equal zero.

Therefore, the total charge of the pipe and the cloth (added together) be zero.