EMI

Question 1

(by pushing the magnet into the solenoid)

Why energy is dissipated in the resistor when magnet is pushed into the solenoid

Answer 1

1) A moving magnet give rise to an increase in magnetic flux in the solenoid,hence induced current in the solenoid
2) According to Lenz law, the emf induced is in the a direction that opposes the increasing flux due to the motion of the magnet.
3) Work done by external force is needed to push the magnet into the solenoid
4) By COE, the work done is converted to thermal energy in the resistor

Question 2

Strong bar magnet oscillating vertically via a helical spring in the air

Answer 2

1) A solenoid experience a change in magnetic flux when the is oscillating vertically in the solenoid, by farady’s law, emf will be induced
2) Since ideal voltmeter has infinite resistance, almost NO induced current flows, thus no opposing magnetic flux will be produced
3) The magnet will continue to oscillate for a long period of time via air friction and internal energy in the spring

Question 3

Farady’s law

Answer 3

The MAGNITUDE of induced emf is directly proportional to the rate of change of MAGNETIC FLUX LINKAGE

Question 4

Lenz Law

Answer 4

Lenz law state that the emf induced is in the direction which opposes the magnetic flux inducing it