Q:-An alternating current is passed through an air-cored solenoid.
An iron core is inserted into the solenoid and then held stationary within the solenoid. The current in the solenoid is now smaller. Explain why the root-mean-square (r.m.s.) value of the current in the solenoid is reduced as a result of inserting the core.
ans:-
(for same current) iron core gives large(r) (rates of change of) flux (linkage) e.m.f induced in solenoid is greater (for same current)
induced e.m.f. opposes applied e.m.f. so current smaller/acts to reduce current
now i understand that inserting iron increases Emf in the solenoid but what does it mean that "the induced emf opposes applied emf so current smaller/acts to reduce current"
is this an application of lenzs law if yes how does lenz law here tell us that current should be decreases when i thought lenzs law only tells us direction of current