Need detailed answer please! so we did our lab on AC fields and in the lab we ad

Question

Need detailed answer please!

so we did our lab on AC fields and in the lab we adjusted the function generator to frequency of 2.5 Hz and we placed a compass next to opening of coil with 800 turns and we observed that when frequency was increased to 2.5 Hz and when the compas was placed near the coil, the compass needle started to rotate in both rotations very quickly but when it was moved further away the compas moved very slowly in both directions. So my question is that why did the compass rotate so quickly when it was moved closer to the coil? it involves some kind of magnetic force acting on the compass or something but I am confused what is acting on the compass and the coil?

The setup for this section is shown below:

Explanation / Answer

a current flowing and the compass is stationary: in the rest frame of the compass there is a flow of negative charge and this generates the magnetic field.

a current flowing and the compass is moving at the electron drift velocity: in the rest frame of the compass the (conduction) electrons are stationary but there is a flow of positive charge in the other direction and this generates the same magnetic field.

a current flowing and the compass is moving at some velocity in between zero and the electron drift velocity: in the rest frame of the compass there is a flow of negative charge in one direction and a flow of positive charge in the other direction and the two flows generate the same magnetic field.

So whether the compass is stationary, moving at the drift velocity or any velocity in between, the deflection of the compass is the same.

this depend on magnetic flux...

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