I am new to electo-magnetism, so i prefer simple language, the problem is:

When we move a magnet relative to a coil such that one of its face is towards or at the coil, an EMF is induced in the coil in such a way that the magnetic field produced by induced current always oppose the motion of magnet, maintaining the magnetic flux, by applying a force on the magnet.

But does the force on magnet depends on parameters of coil, more specifically its resistance??

I thought this after i read: in this situation, the bar magnet experiences a repulsive force due to the induced current. therefore, a person had to do work in moving the magnet AND THE ENERGY IS DISSIPATED BY HEATING PRODUCED BY THE INDUCED CURRENT.

So, two identical coil with different resistances, will have different heating => different work => different force..

probably i have mistaken something, and thnx in advance.


1 Answer 1


I think you are right. For example, if the resistance of the coil is infinite, there is no induced current and no force.

  • $\begingroup$ can we connect it to number of turns in the coil also, zero or infinte turns, something like that in someway $\endgroup$ Commented Feb 9, 2019 at 14:56
  • $\begingroup$ These situations are common in practice. For example, an alternator that does not deliver current (infinite load resistance) does not exert a braking torque on the motor that drives it. When the intensity of the current increases, it is more and more difficult to turn it. English is not my native language and I am not sure I understand your questions ?. $\endgroup$ Commented Feb 9, 2019 at 15:04
  • $\begingroup$ thnx, i think i am done :) and i have same situation in English.. $\endgroup$ Commented Feb 9, 2019 at 15:06
  • $\begingroup$ I think you are right in steady-state but in transient there must be force because if the loop is interrupted with a capacitor, so that the total loop resistance is infinite, there will be conduction currents fluctuating back and forth over the wire. $\endgroup$
    – hyportnex
    Commented Feb 9, 2019 at 15:35
  • $\begingroup$ I assumed there was no capacity, just R. (Of that the time $RC$ was very short compared with the other characteristic time of the problem). $\endgroup$ Commented Feb 9, 2019 at 15:45

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