A diamagnetic substance is placed in the middle between two magnetic poles. If allowed to rotate, explain why the specimen comes to rest with its axis perpendicular to the field.

A copper disc is allowed to swing through the two poles of a U-shaped magnet. Explain what you expect to observe.

A metal rod of length l is placed normal to a uniform magnetic field B. The rod moves with velocity v perpendicular to the field. Show that motional emf across its ends is Blv.

Mohan wants to buy a trapezium shaped field. Its side along the river is parallel to and twice the side along the road. If the area of this field is 10500m^2 and the perpendicular distance between the two parallel sides is 100m, find the length of the side along the river.

A wheel with 25 metallic spokes each 0.4m long is rotated with a speed of 150 rev//min in a plane normal to the horizontal components of earth's magnetic field H_B at a place. If H_E=0.4G at the place, what is the induced emf between the axle and the rim of the wheel?