Charge q is uniformly spread on a thin ring of radius R. The ring rotates about its axis with a uniform frequency $$f$$ Hz. The magnitude of magnetic induction at the center of the ring is

Under the influence of a uniform magnetic field, a charged particle moves with constant speed v in a circle of radius R. The time period of rotation of the particle

A galvanometer havings a coil resistance of 60 $$\Omega $$ shows full scale deflection when a current of 1.0 amp passes through it. It can be converted into an ammeter to read currents upto 5.0 amp by

The magnetic force acting on a charged particle of charge $$-$$2 $$\mu $$C in a magnetic frield of 2 T acting in y direction, when the particle velocity is $$\left( {2\widehat i + 3\widehat j} \right) \times {10^6}\,m{s^{ - 1}}$$