I know that when a wire is moving in a magnetic field, there is an induced EMF due to the change in area, therefore, a change in magnetic flux.

However, what if things we're switched?

Fixing the wire and moving the magnet instead(the magnetic field) will the induced EMF be the same? Assuming the rate of change(or velocity) is the same as the conductor? The magnet is moving at the same velocity as the conductor used to in the previous case, while the cross-sectional area is the same and magnetic field is.

  • 2
    $\begingroup$ Yes, it is the same. As Einstein said "It is all relative." So it is just the relative motion that matters, not if the wire or the magnet is moving. $\endgroup$
    – MaxW
    Dec 24, 2015 at 0:46

1 Answer 1


Of course it is the same. There is no preferred system of reference, and if you sit in a train that is passing by the experiment with 100 mph, you would still see the same thing.

Just imagine that you are tiny and sit on the magnet, and the 'moving' magnet is not moving for you (and actually, you sit on the earth, and it is moving).

The frame of reference does not influence physical laws and their effects.

  • $\begingroup$ At a sufficiently high speed, relativistic effects will make a difference. The electric and magnetic forces are actually the same force, viewed from different frames of reference. The physical effects would be the same, but a relativistic observer would disagree about which force caused them. $\endgroup$
    – user235504
    Dec 24, 2015 at 5:54

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