Question

a-Explain what happens when the magnet moves through the coil at different speeds

b-How this affects the brightness of the bulb and the magnitude & sign of the voltage.

c-Explain the difference between moving the magnet through the coil from the right side versus the left side.

d-Explain the difference between moving magnet through the big coil versus the smaller coil.

Answer 1

a)

When the magnet moves near the coil, the magnetic flux entering the coil changes with time and as per magnetic laws, changing magnetic flux causes current to flow in the coil. Thus the faster the magnet moves, the higher is the rate of change of magnetic flux, the higher is the current produced.

b)

If the speed is more, the current induced is more, thus the brighter the bulb will glow. The emf induced in the coil depends on the speed of the motion of magnet and thus higher the magnet speed, more is the emf induced as

i.e. emf induced is change in flux per unit time.

c)

As per Lenz law, the moving magnet induces a current in the coil such as to oppose any change in the flux. So if the coil is moved from right to left in the coil, the current will be produced to counter either south or north pole whichever is facing towards the coil. When the same coil and magnet are used and the magnet enters from the left side, the opposite pole of what was entering the right side will enter in the coil first and thus the current will be produced in the different or opposite direction as compared to earlier.

d)

When the coil area is big, more flux enters the coil compared to the smaller coil thus the motion of magnet causes more change in flux compared to the smaller thus inducing more current