The figure shows two parallel equipotential surfaces $A$ and $B$ kept a small distance $r$ apart from each other. $A$ point charge of $q$ coulomb is taken from the surface $A$ to $B$. The amount of net work done will be
$ - \frac{1}{{4\pi {\varepsilon _0}}}\frac{q}{r}$
$ \frac{1}{{4\pi {\varepsilon _0}}}\frac{q}{r^2}$
$- \frac{1}{{4\pi {\varepsilon _0}}}\frac{q}{r^2}$
Zero
A capacitor of capacitance $C_0$ is charged to a potential $V_0$ and is connected with another capacitor of capacitance $C$ as shown. After closing the switch $S$, the common potential across the two capacitors becomes $V$. The capacitance $C$ is given by
Two condensers, one of capacity $C$ and the other of capacity $\frac{C}{2}$ , are connected to a $V\, volt$ battery, as shown. The work done in charging fully both the condensers is
A capacitor of capacitance $1$ $\mu F$ with stands the maximum voltages $6$ $KV$ while a capacitor of capacitance $2.0$ $\mu F$ with stands the maximum voltage $=$ $4\,KV$. if the two capacitors are connected in series, then the two capacitors combined can take up a maximum voltage of......$KV$
The electric flux from a cube of edge $l$ is $\phi $. If an edge of the cube is made $2l$ and the charge enclosed is halved, its value will be
A parallel plate capacitor has circular plates of $10\, cm$ radius separated by an air-gap of $1\, mm$ . It is charged by connecting the plates to a $100\, volt$ battery. Then the change in energy stored in the capacitor when the plates are moved to a distance of $1\, cm$ and the plates are maintained in connection with the battery, is