A small rectangular loop of wire is pulled with a steady speed out of a region where…
PHYSICS · Subjective · A Level · Physics · Fields and their consequences · Fields and their consequences
Problem
A small rectangular loop of wire is pulled with a steady speed out of a region where a uniform magnetic field B is directed normally into the plane of the loop. The field exists only inside a long solenoid and is practically zero outside. The external pulling agent supplies the mechanical effort required to bring the loop completely outside the solenoid.
(a) State Lenz’s law.
(b) Explain, without using any equations, why a pulling force must be applied on the loop even though the magnetic field outside the solenoid is negligibly small.
(c) Describe the complete chain of energy conversion that takes place from the instant the loop starts leaving the solenoid till it is completely outside.
(d) How would your answer to part (b) change if the loop were moved faster? Give reasons.