Consider a metal ring kept on the top of a fixed solenoid (say on a cardboard) (Fig. EP 6.14). The centre of the ring coincides with the axis of the solenoid. If the current is suddenly switched on, the metal ring jumps up. Explain.

Consider a metal rign kept on top of fixed solenoid carrying a current as shown in the figure . The centre of the ring coincides with the axis of the solenoid. If the current is suddenly switched off, what will happen to the ring?

Consider a magnet surrounded by a wire with an on/off switch S (Fig. EP 6.11). If the switch is thrown from the off position (open circuit) to the on position (closed circuit), will a current flow in the circuit? Explain.

A conducting rod of 1 m length is rotated with a frequency of 50 rev/s, with one end hinged at the centre and the other end at the circumference of a circular metallic ring of radius 1 m, about an axis passing through the centre and perpendicular to the plane of the ring. A constant and uniform magnetic field of 1 T parallel to the axis is present everywhere. What is the emf between the centre and the metallic ring?

A copper rod of length 2 m fixed at one end is rotating with an angular speed 300 rad s^-1 about an axis normal to the rod and passing thorugh its fixed end. The other end of the end. The other end of the rod is in contact with a circulr metallic ring. A constant magnetic field of 0.4 T parallel to the axis exists everywhere. calculate the e.m.f. developed between the centre and the ring.

A 1.0 m long metallic rod is rotated with an angular frequency of 400 rad s^-1 about an axis normal to the rod passing through its one end. The other end of the rod is in contact with a circular metallic ring. A constant and uniform magnetic field of 0.5 T parallel to the axis exists everywhere. Calculate the emf developed between the centre and the ring.

A positively charged thin metal ring of radius R is fixed in the xy plane with its centre at the origin O. A negatively charged particle P is released from rest at the point (0, 0, z_0 ) where z_0gt0 . Then the motion of P is

A closely wound solenoid of 2000 turns and area of cross-section 1.6 xx 10^1 m^2 . carrying a current of 4.0 A, is suspended through its centre allowing it to turn in a horizontal plane. What is the force and torque on the solenoid if a uniform horizontal magnetic field of 7.5 x 10^2 T is set up at an angle of 30^@ with the axis of the solenoid?