A parallel plate capacitor is connected to a battery as shown in Fig. 2.5. Consider two situations:

A: Key K is kept closed and plates of capacitors are moved apart using insulating handle.

B: Key K is opened and plates of capacitors are moved apart using insulating handle.

Choose the correct option(s).

During A, when K is kept closed and plates of the capacitor are moved apart, the distance between them increases, which in turn decreases the capacitance because it is inversely proportional to the distance between the plates.

Here is the permittivity of free space, A is the area of cross-section of the plates and d is the distance between the plates.

However, the potential difference across the two plates remains the same because the battery is constantly maintaining it. Since, V is constant and C is decreasing, then using the relation Q=CV, we can note that Q will also decrease. Thus, option (c) is correct.

During B, when K is kept open and plates of capacitors are moved apart using insulating handles, then the capacitor is already charged, so Q will remain constant. But capacitance is decreasing so V will increase since V=Q/C. Thus, option (d) is correct.

After the above analysis, it is quite clear that options (a) and (b) are incorrect.