PHYSICS · Subjective · A Level · Physics · Fields and their consequences · Fields and their consequences
Problem
A square coil of N tightly wound turns, each of side a, is fixed in a uniform magnetic field B which is perpendicular to the plane of the coil. The ends of the coil are connected to a resistor R. The magnetic field in the region is reduced uniformly to zero in a time interval Δt.
(a) Calculate the magnitude of the total charge that passes through the resistor during the interval Δt.
(b) Find the total heat produced in the resistor in this process.
(c) Determine the mechanical work done by the external agency responsible for reducing the magnetic field, and show that this work is numerically equal to the heat obtained in part (b). Comment on the result with reference to the principle of conservation of energy.