On increasing the plate separation of a charged condenser, the energy

A capacitor $4\,\mu F$ charged to $50\, V$ is connected to another capacitor of $2\,\mu F$ charged to $100 \,V$ with plates of like charges connected together. The total energy before and after connection in multiples of $({10^{ - 2}}\,J)$ is

An electron with kinetic energy $K _{1}$ enters between parallel plates of a capacitor at an angle $'\alpha'$ with the plates. It leaves the plates at angle $' \beta '$ with kinetic energy $K _{2}$. Then the ratio of kinetic energies $K _{1}: K _{2}$ will be ....... .

Two small spheres each carrying a charge $q$ are placed $r$ metre apart. If one of the spheres is taken around the other one in a circular path of radius $r$, the work done will be equal to

Two capacitors each of $1\,\mu F$ capacitance are connected in parallel and are then charged by $200\;volts$ $d.c.$ supply. The total energy of their charges (in $joules$) is

A charge of $40\,\mu \,C$ is given to a capacitor having capacitance $C = 10\,\mu \,F$. The stored energy in ergs is