Question

Lenz's law explains the induced electromagnetic force so that the direction of the induced conductor is vertical or opposite?

Answer 1

Lenz's law states that the direction of an induced e.m.f. will be such that if it were to cause a current to flow in a conductor in an external circuit, then that current would generate a field that would oppose the change that created it.

Consider a solenoid and a bar magnet, as in Figure 1. Moving the bar magnet into the solenoid induces an e.m.f. in the solenoid (according to Faraday's law), and because the circuit is closed, a current flows and a magnetic field is induced.

First think about what would happen if the opposite of Lenz's Law were true. Then the direction of the induced e.m.f. would be such that its magnetic field at the end of the solenoid nearest the N pole of the magnet, would resemble that of a south pole, and so the bar magnet would experience an attractive force directed into the solenoid. This would cause the bar magnet to accelerate, increasing the rate of change of magnetic flux linkage in the coil and consequently increasing the induced e.m.f., the current and the attractive force.

In this scenario energy is being produced from nothing. Due to conservation of energy this is not possible and therefore the magnetic field due to the induced e.m.f. in the solenoid must oppose the magnetic field due to the bar magnet, as predicted by Lenz's law, as in Figure 1. This illustrates that Lenz's law is a result of energy conservation.

Lenz's law can be incorporated into Faraday's law to give induced e.m.f.=−?(ΔΦ/Δ?) induced e.m.f.=−N(ΔΦ/Δt) since the sense of the e.m.f is opposite to the direction of the rate of change of magnetic flux linkage.

Figure. 1