A large solid sphere with uniformly distributed positive charge has a smooth narrow tunnel through its centre. A small particle with negative charge, initially at rest far from the sphere, approaches it along the line of tunnel, reaches its surface with a speed v, and passes through the tunnel. Its speed at the centre of the sphere will be

Two identical metal balls with charges +2Q and -Q are separated by some distance, and exert a force F on each other. They are joined by a conducting wire, which is then removed. The force between them will now be

Electric potential of earth is taken to be zero because earth is a good

A 100 μF capacitor is charged to a potential difference of 50 V, the charging battery then being disconnected. The capacitor is then connected to a second capacitor. If the measured potential difference drops to 35 V, the capacitance of the second capacitor is

On moving a charge of 20 coulomb by 2cm, 2 J of work is done, then the potential difference between the points is

The electric potential V at any point (x₁, y₁, z₁) in space is given by V = 4x² volt. The electric field at (1, 0, 2) m in Vm^-1 is

Capacitance (in F) of a spherical conductor with radius 1 m is

Two spherical conductors A and B of radii 1mm and 2mm are separated by a distance of 5 cm and are uniformly charged. If the spheres are connected by a conducting wire then the equilibrium condition, the ratio of the magnitude of the electric fields at the surfaces of spheres A and B is

The study of the effects associated with electric charges at rest is called 

The dielectric strength of air at NTP is 3 × 10⁶ V/m. The maximum charge that can be given to a spherical conductor of radius 3 m is