An electron is accelerated through a potential difference of $2.5 \ V$. The energy gained by the electron is . . . . . . . (Charge of an electron = $1.6 \times 10^{-19} \ C$)

Particles $A$ and $B$ have charges $+q$ and $+4q$ respectively. Both have the same mass $m$. If they are released from rest and accelerated through the same potential difference $V$,the ratio of their velocities $v_A/v_B$ is:

Calculate the electric potential on the axis of a ring of radius $R$ due to a charge $Q$ uniformly distributed along it.

$A$ proton is about $1840$ times heavier than an electron. When it is accelerated by a potential difference of $1\, kV$,its kinetic energy will be......$keV$.

An infinite number of charges,each equal to $0.2\,\mu C$,are arranged in a line at distances $1\,m, 2\,m, 4\,m, 8\,m, \dots$ from a fixed point. The potential at the fixed point is $......\,kV$.

Two spheres $A$ and $B$ of radius $a$ and $b$ respectively are at the same electric potential. The ratio of the surface charge densities of $A$ and $B$ is