A ring of mass m, radius r having charge q uniformly distributed over it and free to rotate about its own axis is placed in a region having a magnetic field B parallel to its axis. If the magnetic field is suddenly switched off, the angular velocity acquired by the ring is:

A thin non conducting horizontal disc of mass m having total charge q distributed uniformly over its surface, can rotate freely about its own axis. Initially when the disc is stationery a magnetic field B directed perpendicular to the plane is switched on at t=0 . Find the angular velocity omega acquired by disc as a function of time, if B=kt , where t is time.

A thin non-conducting ring of mass m carrying a charge q can freely rotate about its axis. At t = 0 , the ring was at rest and no magnetic field was present. Then suddenly a magnetic field B was set perpendicular to the plane. Find the angular velocity acquired by the ring.

A non-conducting ring of mass m and radius R has a charge Q uniformly distributed over its circumference. The ring is placed on a rough horizontal surface such that plane of the ring is parallel to the surface. A vertical magnetic field B = B_0t^2 tesla is switched on. After 2 a from switching on the magnetic field the ring is just about to rotate about vertical axis through its centre. (a) Find friction coefficient mu between the ring and the surface. (b) If magnetic field is switched off after 4 s , then find the angle rotated by the ring before coming to stop after switching off the magnetic field.

A circular wire of radius r rotates about its own axis with angular speed w in a magnetic field B perpendicular to its plane, then the induced e.m.f. is

A ring of mass m and radius R is given a charge q. It is then rotated about its axis with angular velocity omega .Find (ii) Magnetic field produced at the centre of ring.

A non - conducting ring of mass m = 4 kg and radius R = 10 cm has charge Q = 2 C uniformly distributed over its circumference. The ring is placed on a rough horizontal surface such that the plane of the ring is parallel to the surface. A vertical magnetic field B=4t^(3)T is switched on at t = 0. At t = 5 s ring starts to rotate about the vertical axis through the centre. The coefficient of friction between the ring and the surface is found to be (k)/(24) . Then the value of k is

A hollow sphere has charge 'q' which is uniformly distributed over its surface and rotating about its axis .Find the magnetic moment of the sphere

A thin non-conducting ring of mass m carrying a charge q can freely rotate about its axis. At the initial moment, the ring was at rest and no magnetic field was present. Then a uniform magnetic field was switched on, which was perpendicular to the plane of the ring and increased with time according to a certain law: (dB)/(dt) = k . Find the angular velocity omega of the ring as a function of k .

A thin non-conducting ring of mass m carrying a charge q can freely rotate about its axis. At the initial moment the ring was at rest and no magnetic field was present. Then a practically unifrom magnetic field was switched on, which was perpendicular to the planeof the ring and increased with time according to a certain law B (t) , Find the angluar velocity omega of the ring as a function of the induction B(t) .