A rectangular conducting frame of width and length (with ) has a total resistance
PHYSICS · Multi-part · A Level · Physics · Fields and their consequences · Fields and their consequences
Problem
A rectangular conducting frame of width w and length l (with l≫w) has a total resistance R. The frame is pulled with a steady speed v into a region of uniform magnetic field B that is perpendicular to the plane of the frame. Initially the left edge of the frame just touches the boundary of the field region; the right edge is still outside.
Attempt the following parts in sequence.
(i) If x is the length of the frame that has entered the field at an instant t, derive an expression for the induced emf E(t) in terms of B, v and w.
(ii) State the direction of the induced current during (a) the entry of the frame into the field and (b) its exit from the field.
(iii) Show that the mechanical power required to pull the frame at the constant speed v is equal to the rate at which electrical energy is dissipated as heat in the frame.