Question

The plates of a charged condenser are connected to a voltmeter. If the plates are moved apart, the reading of voltmeter will

• A. increase
• B. decrease
• C. remain unchanged
• D. information is insufficient

Answer 1

Answer: (A)

$q=CV=$ constant $\dots$ (i)
Capacitance ( C) of a parallel plate capacitor is given by
$C=\frac{{\epsilon }_{0}A}{d}$
where $A$ is area of plates and $d$ the separation between them.
From Eqs. (i) and (ii), we have
$q=\frac{{\epsilon }_{0}A}{d}.V=$ constant
When plates are moved apart, $d$ increases,
hence value of $C$ decreases and in order that charge $(q)$ remains constant $V$ increases.