Question

When a wire loop is rotated in a magnetic field, the direction of induced emf changes once in each

• A. changes every 1/4 revolution
• B. does not change
• C. change every 1/2 revolution
• D. changes every 1 revolution

Answer 1

The correct option is C

change every 1/2 revolution

Magnetic Field:

The magnetic effect on electric charges, electric currents, and magnetic materials is described by a magnetic field, which is a vector field. In a magnetic field, a moving charge experiences a force that is perpendicular to both its own velocity and the magnetic field.

Magnetic Flux:

The number of magnetic field lines traveling through a closed surface is known as magnetic flux. It calculates the total magnetic field that passes across a specific surface area.

The flux of the magnetic field through the loop

$\mathrm{\varphi }=\mathrm{B}.\mathrm{Acos\omega t}$

Where,

1. $\mathrm{\varphi }$ is the magnetic flux.
2. $\mathrm{B}$ is the magnetic field
3. $\mathrm{A}$ is the area
4. $\mathrm{\omega t}$ the angle at which the field lines pass through the given surface area

When an electrical conductor is put into a magnetic field, emf is induced in it due to its dynamic interaction with the magnetic field.

$$\begin{gathered} \mathrm{Emf}=-\frac{\mathrm{dt}}{\mathrm{d\varphi }} \\ =\mathrm{B}.\mathrm{A\omega sin\omega t} \end{gathered}$$

$$\begin{gathered} \mathrm{\omega t}=0\mathrm{to}\mathrm{\pi },\mathrm{sin\omega t}=+\mathrm{ve} \\ \mathrm{\omega t}=\mathrm{\pi }\mathrm{to}2\mathrm{\pi },\mathrm{sin\omega t}=-\mathrm{ve} \end{gathered}$$

As a result, the induced e.m.f. orientation changes once every $\frac{1}{2}$ revolution.

Therefore, the correct option is C.