A circular coil of 200 turns and radius 5.0 cm has a total resistance of 10 Ω
PHYSICS · Multi-part · A Level · Physics · Fields and their consequences · Fields and their consequences
Problem
A circular coil of 200 turns and radius 5.0 cm has a total resistance of 10 Ω. The coil is placed coaxially around one pole of a bar magnet. The normal to the plane of the coil is along the axis of the magnet. The magnet is suddenly pulled away so that the magnetic flux linked with each turn decreases uniformly from 5.0 mWb to zero in 0.20 s.
(i) Calculate the magnitude of the average emf induced in the coil during the withdrawal of the magnet.
(ii) Determine the total charge that passes through the coil in this interval.
(iii) Compute the total thermal energy produced in the coil due to the induced current.
(iv) Find the minimum mechanical work that must be done in pulling the magnet away if no other energy losses occur, and state the physical principle that relates your answers in parts (iii) and (iv).