0
$\begingroup$

Suppose I have an infinite wire and close by I place a loop which has increasing current. The wire and the loop is fixed . Now an emf will be induced in the infinite wire which in turn induces a current to oppose the changing magnetic field . My question is why this emf is induced in the infinite wire even though the wire is stationary( in order for motional emf to be induced) and also there is no loop formed by the infinite wire? How to define the flux change in this condition for the infinite wire in order to apply faraday's law to calculate emf?

$\endgroup$

1 Answer 1

2
$\begingroup$

There is no motional EMF, because the wires don't move.

In the straight wire there will be some induced EMF. This is due to induced electric field, produced by the accelerated current in the loop.

There need not be any loop, induced EMF is defined as integral of induced electric field over some path; this path need not be closed.

If the straight wire is finite, it has two ends not connected to anything, and there will still be induced EMF in the straight wire. Current will be almost zero, because the ends are open and allow for redistribution of charge in such a way that it almost cancels the effect of the EMF. Potential difference and induced EMF will cancel each other.

$\endgroup$
2
  • $\begingroup$ But why the electric field is induced since there is no change in flux? $\endgroup$ Jun 16, 2023 at 11:19
  • $\begingroup$ Induced electric field is generated by accelerated charges (that make up the current that is changing in time). Flux and change in flux are secondary - one must first define closed path in space. For example, we can define closed path that goes through the straight wire, and returns back outside the wire. Flux through such closed path changes in time, because magnetic field of the changing current changes in time. $\endgroup$ Jun 16, 2023 at 11:26

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.