Suppose we want to perform an electromagnetic induction. So we have a coil & a magnet. There is no gravitational force working on them. So we roll the magnet horizontally in an axis in front of the coil. If there is absolutely no gravitational force working on it, it will roll forever. So we will get infinte electricity. How is this possible?

Or will the magnet stop rolling due to some electromagnetic reason? Please explain.


The moving magnet will change the magnetic flux through the coil and so there will be an induced emf in the coil.
Assuming the coil is part of a complete electrical circuit then an induced current will flow in the circuit.

By Lenz's law that induced current will be in such a direct as to try and oppose the change producing it which in this case is the moving magnet.

So due to the induced current there will be a force on the magnet which will reduce the kinetic energy of the magnet ie the magnet will slow down.

The electrical energy produced by the moving magnet will be equal to the kinetic energy lost by the magnet which will eventually stop.

  • $\begingroup$ How much time it will take the magnet to stop? Can u give me the mathematical calculation? $\endgroup$ – Theoretical Feb 11 '18 at 11:15
  • $\begingroup$ To do such a calculation is very difficult. $\endgroup$ – Farcher Feb 11 '18 at 11:18
  • $\begingroup$ @Catcher Can you give a website's address where I can find the dervations of physics formulas? $\endgroup$ – Theoretical Feb 11 '18 at 11:46

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