Electrostatics 5 Question 40
42. A parallel plate capacitor is charged and the charging battery is then disconnected. If the plates of the capacitor are moved farther apart by means of insulating handles
(1987, 2M)
(a) the charge on the capacitor increases
(b) the voltage across the plates increases
(c) the capacitance increases
(d) the electrostatic energy stored in the capacitor increases
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Solution:
- Charging battery is removed. Therefore, $q=$ constant
Distance between the plates is increased. Therefore, $C$ decreases.
Now, $V=q / C, q$ is constant and $C$ is decreasing.
Therefore, $V$ should increase.
$U=\frac{1}{2} \frac{q^{2}}{C}$ again $q$ is constant and $C$ is decreasing.
Therefore $U$ should increase.
$\therefore$ Correct options are (b) and (d).
