In the figure a potential of $+ 1200\, V$ is given to point $A$ and point $B$ is earthed, what is the potential at the point $P$....$V$
$100$
$200$
$400$
$600$
If on the concentric hollow spheres of radii $r$ and $R( > r)$ the charge $Q$ is distributed such that their surface densities are same then the potential at their common centre is
The energy stored in the capacitor is $'U'$. If an uncharged capacitor of same capacity is connected in parallel with it, then energy stored in each capacitor is
The amount of heat liberated in the circuit after closing the switch $S$ .
The work done in placing a charge of $8 \times 10^{-18}$ coulomb on a condenser of capacity $100\, micro-farad$ is
A charge $q$ is placed at the centre of the line joining two equal charges $Q$. The system of the three charges will be in equilibrium, if $q$ is equal to