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  • What is happening when delta x of this loop increases? Give me a theoretical idea and how is emf increasing? I know that flux is changing but I think that the rails on which conductor rod is moving is not contributing that much to induced emf

  • What is induced emf actually in this case is it the energy with which charges are moving or the increasing electric field in conductor because of the charge accumulation at the corners of conductor creating a region acting as source for energy

  • $\begingroup$ Faraday's Law is the key to this problem. You know that the magnetic flux within the loop is increasing as the loop widens; what happens? $\endgroup$ Dec 24, 2016 at 5:15
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    $\begingroup$ @probably_someone i know faraday law tells us that then emf will be generated but in what sense by increasing the number of opposite charges at two opposite ends of conductor or by givnig charges more energy to flow $\endgroup$
    – Mahin
    Dec 24, 2016 at 12:31

1 Answer 1


The induced emf blv is called motional emf. thus we are able to produce induced emf by moving a conductor instead of varying magnetic field that is, by changing the magnetic flux enclosed by the circuit. it is possible to explain the motional emf expression by invokin the lorentz force actin on the free charge carries of conductor.Consider any arbitrary charge q in the conductor. When the rod moves with speed v, the charge will also be moving with speed v in the magnetic field B. The lorrentz force on this charge is qvb in magnitude, and its direction, irrespective of their position in the rod.

It is not obvious how an emf is induced when a conductor is stationary and the magnetic field is changing-a fact which Faraday verified by numerous experiments. In the case of a stationary conductor, theforce on its charges given by

F =q(E + v×B)=q E

since v=0 , thus any force on the charge must arise from the electric field term E alone . Therefore, to explain the existence of induced emf or induced current, we must assume that a time-varying magnetic field generates an electric field . However we hasten to add that electric field produced by static electric charges have properties different from those produced by time varying magnetic fields. we know that charges in motion(current) can exert force/torque on a statiionary magnet. conversely, a bar magnet in motion(or more generally, a changing magnetic field) can exert a force on the stationary charge. this is the fundamental significance of the Faraday's discovery. Electricity and magnetism are related.

  • $\begingroup$ btw The induced emf is blv. $\endgroup$ Dec 28, 2016 at 19:50

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