A square of side ‘$a$’ has charge $Q$ at its centre and charge ‘$q$’ at one of the corners. The work required to be done in moving the charge ‘$q$’ from the corner to the diagonally opposite corner is
Zero
$\frac{{Qq}}{{4\pi { \in _0}a}}$
$\frac{{Qq\sqrt 2 }}{{4\pi { \in _0}a}}$
$\frac{{Qq}}{{2\pi { \in _0}a}}$
Three charges $-q, Q$ and $-q$ are placed respectively at equal distances on a straight line. If the potential energy of the system of three charges is zero, then what is the ratio of $Q: q$ ?
A particle of mass $m$ having negative charge $q$ move along an ellipse around a fixed positive charge $Q$ so that its maximum and minimum distances from fixed charge are equal to $r_1$ and $r_2$ respectively. The angular momentum $L$ of this particle is
For equal point charges $Q$ each are placed in the $xy$ plane at $(0, 2), (4, 2), (4, -2)$ and $(0, -2)$. The work required to put a fifth change $Q$ at the origin of the coordinate system will be
In the electric field of a point charge $q$, a certain charge is carried from point $A$ to $B$, $C$, $D$ and $E$. Then the work done
Two equal point charges are fixed at $x = - a$ and $x = + a$ on the $x-$axis. Another point charge $Q$ is placed at the origin. The Change in the electrical potential energy of $Q$, when it is displaced by a small distance $x$ along the $x$-axis, is approximately proportional to