Question

What is Induced EMF?

Answer 1

Induced EMF

1. Induced EMF: If the magnetic flux through a coil is changed, a voltage will be produced. This voltage is known as the induced emf.

Induced EMF can be created in two ways:

1. If an electric current conductor moves in a magnetic field then an induced emf is produced.
2. If a magnetic field is moving around an electric field then an induced EMF is produced

The mathematical expression for induced emf is

1. For a rod
   $$\begin{gathered} \mathrm{induced}\mathrm{emf}=\mathrm{magnetic}\mathrm{field}\times \mathrm{length}\mathrm{of}\mathrm{the}\mathrm{conductor}\times \mathrm{speed}\mathrm{of}\mathrm{the}\mathrm{moving}\mathrm{object}\mathrm{relative}\mathrm{to}\mathrm{the}\mathrm{magnetic}\mathrm{field} \\ \mathrm{e}=\mathrm{BLv} \end{gathered}$$
   From the above equations, we can say,
   4.1 The number of turns in the coil is directly proportional to the induced emf
   4.2 The magnetic field strength is directly proportional to the induced emf
   4.3 The speed of the relative motion between the coil and the magnet is directly proportional to the induced emf
2. According to Lenz's law, 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 when the current flows in it.
   $$\begin{gathered} \mathrm{emf}=\mathrm{number}\mathrm{of}\mathrm{turns}\times \frac{\mathrm{change}\mathrm{in}\mathrm{flux}}{\mathrm{change}\mathrm{in}\mathrm{time}} \\ \mathrm{e}=-\mathrm{N}\frac{\mathrm{d\varphi }}{\mathrm{dt}} \end{gathered}$$
   From the above equations, we can say,
3. Hence, the rate of change of flux is directly proportional to the induced emf