Question

Explain the sign of emf using Lenz’s law.

Answer 1

First we need to know what an Len’s law stats. We need to know that when an emf is generated by the change magnetic the polarity of the induced emf is such that it produces a current and that current produces the magnetic field which produces it.

Complete step by step solution:
This law states that the induced electromotive force with different polarities induces a current whose magnetic field opposes the change in magnetic flux through the loop in order to ensure that the original flux is maintained through the loop whenever current flows through it.
The negative sign that is used in this faraday’s law of electromagnetic induction induces that the induced emf and the change in the magnetic flux have opposite signs.
Mathematically we can write it as,
$E = - N\dfrac{{d\phi }}{{dt}}$
Where,
E is the electromagnetic force.
$\phi$ is the flux linked with the coil due to the magnetic field.
$N$ is the number of turns in the coil.
This law obeys the law of conservation of energy that is if the direction of the magnetic field that creates the current and the magnetic field of the current in the conductor are the same due to which the two magnetic fields would add up and it produces the current of twice its magnitude creating more magnetic files.

Note:
Remember this special case if all parts of the loop are moving with uniform translational velocity or in an uniform magnetic field then the loop observes no change in the magnetic flux passing through it and the induced electromotive force is equal to zero. And note that this case is similar to the rigid loop that is moving in a uniform magnetic field.