A positive charge q is placed in a spherical cavity made in a positively charged sphere. The centres of sphere and cavity are displaced by a small distance `vec(l)`. Force on charge q is :

A cavity of radius r is made inside a solid sphere. The volume charge density of the remaining sphere is rho . An electron (charge e, mass m) is released inside the cavity from point P as shown in figure. The centre of sphere and center of cavity are separated by a distance a. The time after which the electron again touches the sphere is

Asseration: A point charge q is placed at centre of spherical cavity inside a spherical conductor as shown. Another point charge Q is placed outside the conductor as shown. Now as the point charge Q is pushed away from conductor, the potential difference (V_(A) - V_(B)) between two points A and B within the cavity of sphere remains constant. Reason: The electric field due to charges on outer surface of conductor and outside the conductor is zero at all points inside teh conductor.

There is a cubical cavity inside a conducting sphere of radius R. A positive point charge Q is placed at the centre of the cube and another positive charge q is placed at a distance 1(gtR) from the centre of the sphere. The sphere is earthed Net charge on the outer surface of conducting sphere is

A metallic sphere having no net charge is placed near a finite metal plate carrying a positive charge. The electric force on the sphere will be