An ideal cell is connected across a capacitor as shown in figure. The initial separation between the plates of a parallel plate capacitor is d. The lower plate is pulled down with a uniform velocity v. Neglect the resistance of the cirucit. Then the variation of charge on capacitor with time is given by

Options

A.
B.
C.
D.

Answer

B

Explanation

Let the area of parallel plate be A. Then the capacitance of the capacitor at any time t is
`C=(A epsilon_(0))/(d+vt)`. Hence the charge on capacitor
At any instant t is `q=CE=(A epsilon_(0))/(d+vt)E`.
Or `q(d+vt)=A epsilon_(0)E`=Constant
Therefore the graph showing the variation of q with t is