Question

A coil is moved towards a stationary magnet. The voltage induced in the coil depends on

• A. area of the coil.
• B. the speed with which the coil is moved towards the bar magnet.
• C. a number of turns of the coil.
• D. All the above

Answer 1

The correct option is D

All the above

The explanation for option A:

1. The magnetic flux is a measure of the number of magnetic field lines passing through an area.
2. If the magnetic flux through a coil is changed, a voltage will be produced. This voltage is known as the induced emf.
3. If a loop of wire with an area A is in a magnetic field B, the magnetic flux is given as $\varphi =BA\cos \theta$ where $B$ is a magnetic field, $A$ is an area of the coil and $\theta$ is the angle between $B$ and $A$.
4. Induced emf is directly proportional to the area of the coil.

The explanation for option B:

1. The induced emf in a coil is given by $\epsilon =-N\frac{d\varphi }{dt}$ where $N$ is the number of turns, $\frac{d\varphi }{dt}$ is a change in flux in a certain time interval.
2. The negative sign indicates that the emf induced in the coil acts to oppose any change in the magnetic flux.
3. Induced emf is directly proportional to the speed with which the coil is moved towards the bar magnet.
4. When we increase the speed the change in magnetic flux also increases that is $\frac{d\varphi }{dt}$

The explanation for option C:

1. The induced emf in a coil is given by $\epsilon =-N\frac{d\varphi }{dt}$ where $N$ is the number of turns, $\frac{d\varphi }{dt}$ is a change in flux in a certain time interval.
2. The negative sign indicates that the emf induced in the coil acts to oppose any change in the magnetic flux.
3. Induced emf is directly proportional to the number of turns of the coil.

Hence, A coil is moved towards a stationary magnet. The voltage induced in the coil depends on the area of the coil, the speed with which the coil is moved towards the bar magnet, and the number of turns of the coil.

Therefore, the correct option is option D.