The conducting spherical shells shown in the figure are connected by a conductor. The capacitance of the system is
$4\pi {\varepsilon _0}\,\frac{{ab}}{{b - a}}$
$4\pi {\varepsilon _0}\,a$
$4\pi {\varepsilon _0}\,b$
$4\pi {\varepsilon _0}\,\frac{{{a^2}}}{{b - a}}$
A hollow metal sphere of radius $5\, cm$ is charged so that the potential on its surface is $10\, V$. The potential at the centre of the sphere is.....$V$
Electric potential at any point is : $V = -5x + 3y + \sqrt {15} z$ ; then the magnitude of electric field is :-
In the figure a capacitor is filled with dielectric. The resultant capacitance is
Three identical dipoles are arranged as shown below. What will be the net electric field at $M$
Two identical balls having like charges and placed at a certain distance apart repel each other with a certain force. They are brought in contact and then moved apart to a distance equal to half their initial separation. The force of repulsion between them increases $4.5$ times in comparison with the initial value. The ratio of the initial charges of the balls is