Coil in magnetic field. Voltage step response

Electrical Engineering Asked by grabantot on October 11, 2020

Say we have a coil in magnetic field as shown below (two empty squares are magnet poles). Now imagine we give some voltage pulse across the terminals.

I wonder how would current (its magnitude and rise/fall times) depend on angle between magnetic induction B and coil axis. What processes are involved? How is it possible to sense coil orientation using it? I also would like to see the equations.

The physical process

The voltage induced by a changing magnetic field is given by Faraday's law. Basically it says

voltage = turns of wire * (rate of change of magnetic flux)

Where magnetic flux basically means the total magnetic field passing through the coil.

If your coil is stationary, the rate of change of magnetic flux due to the magnet is zero. So, in the experiment your propose, the angle will have no effect. You won't be able to sense the magnetic field angle using the coil alone.

That said, you might be able to sense the presence of iron near the coil, because the inductance of the coil will be larger if iron is nearby (which will manifest as a slower rise and slower fall in the current).

Answered by Luke on October 11, 2020