Question

When electrophorus is charged, the electricity is obtained from:
A. Cat’s skin
B. Metallic plate
C. Sole
D. Ebonite plate

Answer 1

Hint: You may recall what exactly an electrophorus is. Then find out the basic structure as well as the working of an electrophorus. Now you could understand where the electricity from an electrophorus is obtained after it gets charged and hence find which among the given options is the right answer.

Complete step by step answer:
In the question, we are asked to find the source of electricity when the electrophorus is charged from the given options. For that let us first understand the basic structure and working of electrophorus.
So, we could electrophorus (electrophore) as a simple manual capacitive electrostatic generator that is used to produce electrostatic charge by the process of electrostatic induction.
Basically, they consist of a dielectric plate along with a metal plate and also an insulating handle. Initially the dielectric plate gets charged on rubbing with fur or cloth. After that we place the metal plate onto it. Now the electrostatic field of the charged dielectric causes the separation of charges in the metal plate.
Development of two regions of charge takes place: positive charge on the side facing the dielectric and negative charge on the side facing up. We could now momentarily ground and hence drain off the negative charge from the side facing up. Now this remaining charge on the metal plate is used after lifting off from the setup.
Therefore, we could say that, when an electrophorus is charged, the electricity is obtained from the metallic plate.

Hence, the answer is option B.

Note:
We know that the universe demands the charge to be conserved. We have seen that electrophorus only separate charges. However work is definitely done on lifting up the lid. The resultant additional energy gets converted into potential energy which further results in charge separation. So by lifting the metal plate, we actually increase the potential difference between the two plates.