The capacitance of a variable capacitor connected to a $10 \mathrm{V}$ battery is changed from $7$ to $3 \mathrm{\mu F}$. Compute energy-change.

The capacitance of a variable radio capacitor can be changed from$50 \mathrm{pF}$ to $950 \mathrm{pF}$ By tuning the dial from $0$ to $180°.$ With the dial set at$180°$, the capacitor is connected to a $400 \mathrm{V}$ Battery. After charging, the capacitor is disconnected from the battery and the dial is turned to$0.$ What is the potential difference across the capacitor when the dial reads $0$?

The capacitance of a variable radio capacitor can be changed from $50 \mathrm{pF}$ to $950 \mathrm{pF}$ by tuning the dial from $0°$ to $180°$. With the dial set at $180°$, the capacitor is connected to a $400 \mathrm{V}$ battery. After charging, the capacitor is disconnected from the battery and the dial is turned to $0°$. How much work is required to turn the dial, if friction is neglected?

Three equal$9 \mathrm{pF}$ capacitors are connected in series. Find the total capacitance of the combination.

Three equal $9 \mathrm{pF}$ Capacitors are connected in series. Find PD across each capacitor if the combination is connected to a $120 \mathrm{V}$ Supply.

Three capacitors of $2 \mathrm{pF}, 3 \mathrm{pF}$ and$4 \mathrm{pF}$ Capacitances are connected in parallel. Find the total capacitance of the combination.

Three capacitors of $2\mathrm{pF}$, $3\mathrm{pF}$and $4\mathrm{pF}$ capacitances are connected in parallel. Find charge on each capacitor if the combination is connected to a $100 \mathrm{V}$ Supply.