A long solenoid is wound uniformly with 800 turns of wire over a length of
PHYSICS · Multi-part · A Level · Physics · Fields and their consequences · Fields and their consequences
Problem
A long solenoid is wound uniformly with 800 turns of wire over a length of 0.40m. A cylindrical rod is fully inserted along the axis of the solenoid. The current in the solenoid is increased to a steady value of 2.5A and maintained for 15s before being switched off. Two different rods are tested separately under identical conditions: one made of soft iron and the other of hard steel.
Answer the following.
(1) Determine the approximate magnitude of the magnetic field inside the solenoid while the current is on. Express your answer to two significant figures.
(2) After the current is switched off, which rod will retain the greater magnetic field? Justify your answer based on material properties.
(3) If the exposure time in the solenoid were doubled while keeping all other parameters the same, predict qualitatively how the remanent magnetization of the hard-steel rod would change, and explain your reasoning.