To demonstrate large emf is induced when direct current is switched off in an inductive circuit.
Changing the magnetic field induces emf. It is electromagnetic induction. It was discovered by Michael Faraday. Faraday’s law of electromagnetic induction is the “Magnitude of induced emf in a circuit is equal to the time rate of change of magnetic flux through the circuit.”
Induced emf (ε)= - dΦ/dt, Φ-magnetic flux through the circuit
A bar magnet brings towards the loop. The magnetic field increases across the loop. To oppose the increase in a magnetic field, a current induces in the loop. The magnetic field of the induced current opposes the approaching magnetic field. Loop’s north pole directly faces the north pole of the magnet to repel the approaching magnetic field. The direction of the induced current in the loop is counter clockwise direction.
Emf is induced in a single isolated coil due to changes in magnetic flux through the coil by varying currents through the same coil. This is self-induction.
Self-inductance of solenoid, L/l =μ0n2A
l- length of solenoid
n- no of turns per unit length
A-Cross sectional area of solenoid
μ0= 4 π x 10 -7 Tm/A