Two coils of self-inductance 2 mH and 8 mH are placed so close together that the effective flux in one coil is completely linked with the other. The mutual inductance between these coils is:
1. 10 mH
2. 6 mH
3. 4 mH
4. 16 mH
In which of the following devices, the eddy current effect is not used?
1. | electric heater |
2. | induction furnace |
3. | magnetic braking in train |
4. | electromagnet |
A \(800\) turn coil of effective area \(0.05~\text{m}^2\) is kept perpendicular to a magnetic field \(5\times 10^{-5}~\text{T}\). When the plane of the coil is rotated by \(90^{\circ}\)around any of its coplanar axis in \(0.1~\text{s}\), the emf induced in the coil will be:
1. | \(0.02~\text{V}\) | 2. | \(2~\text{V}\) |
3. | \(0.2~\text{V}\) | 4. | \(2\times 10^{-3}~\text{V}\) |
1. | the rectangular, circular, and elliptical loops. |
2. | the circular and the elliptical loops. |
3. | only the elliptical loop. |
4. | any of the four loops. |
A conducting circular loop is placed in a uniform magnetic field of \(0.04\) T with its plane perpendicular to the magnetic field. The radius of the loop starts shrinking at a rate of \(2\) mm/s. The induced emf in the loop when the radius is \(2\) cm is:
1. \(3.2\pi ~\mu \text{V}\)
2. \(4.8\pi ~\mu\text{V}\)
3. \(0.8\pi ~\mu \text{V}\)
4. \(1.6\pi ~\mu \text{V}\)
A conducting circular loop is placed in a uniform magnetic field, \(B=0.025~\text{T}\) with its plane perpendicular to the loop. The radius of the loop is made to shrink at a constant rate of \(1~\text{mm s}^{-1}\). The induced emf, when the radius is \(2~\text{cm}\), is:
1. \(2\pi ~\mu\text{V}\)
2. \(\pi ~\mu\text{V}\)
3. \(\dfrac{\pi}{2}~\mu\text{V}\)
4. \(2 ~\mu \text{V}\)
The current \(i\) in a coil varies with time as shown in the figure. The variation of induced emf with time would be:
1. | |
2. | |
3. | 4. |
The current (\(I\)) in the inductance is varying with time (\(t\)) according to the plot shown in the figure.
1. | ![]() |
2. | ![]() |
3. | ![]() |
4. | ![]() |