A parallel plate capacitor is connected to a battery as shown in figure. Consider two situations :
.
A : Key `K` is kept closed and plates of capacitors are moved apart using insulting handle.
B : Key `K` is opened and plates of capacitors are moved apart using insulting handle. Choose the correct options (s).

Options

A. In A : `Q` remains same but `C` changes
B. In B : `V` remains same but `C` changes
C. In A : `V` remains same and hence `Q` changes
D. In B : `Q` remains same and hence `V` changes.

Answer

C, D

Explanation

In Fig, when key `K` si kept closed, condenser `C` is charged to potential `E`. When plates of capacitor are moved apart, its capacity `C = (in_(0) A)/(d)` decreases. As potential of condenser remains same, charge `Q = CE` decreases, Choice (c ) is correct.
Once key `K` is closed condenser gets charged : `Q = CE`. Now, if key `K` is opened battery is disconnected , no more charging can occur, i.e., `Q` remains same. As plates fo capacitor are moved apart, its capacity `C = (in_(0) A)/(d)` decreases. Therefore, its potential `V = Q//C` increases. Choice (d) is correct.