Calculate the self-inductance of a solenoid having \(1000\) turns and length \(1\) m. (The area of cross-section is \(7\) cm2 and \(\mu_r=1000).\)
1. \(888\) H
2. \(0.88\) H
3. \(0.088\) H
4. \(88.8\) H
A rod having length \(l\) and resistance \(R_0\) is moving with speed \(v\) as shown in the figure. The current through the rod is:
1. \(\frac{B l v}{\frac{R_{1} R_{2}}{R_{1} + R_{2}} + R_{0}}\)
2. \(\frac{Blv}{\left(\frac{1}{R_{1}} + \frac{1}{R_{2}} + \frac{1}{R_{o}}\right)^{2}}\)
3. \(\frac{B l v}{R_{1} + R_{2} + R_{0}}\)
4. \(\frac{B l v}{\frac{1}{R_{1}} + \frac{1}{R_{2}} + \frac{1}{R_{0}}}\)
The slotting processes in a metallic sheet results in:
1. | The increase of the resistance in the path for circulation of current. |
2. | Decrease in the strength of eddy current. |
3. | A feeble in the electromagnetic damping. |
4. | All of these |
1. | \(\dfrac{E^{2}}{2 R}\) | 2. | \(\dfrac{E^{2} L}{2 R^{2}}\) |
3. | \(\dfrac{E^{2} L}{R}\) \(\) | 4. | \(\dfrac{E^{2} L}{2 R}\) |
The coefficient of mutual inductance between two coils depends upon:
1. | medium between coils |
2. | separation between coils |
3. | orientation of coils |
4. | All of these |
1. | \(\dfrac{L}{l}\) | 2. | \(\dfrac{l}{L}\) |
3. | \(\dfrac{L^2}{l}\) | 4. | \(\dfrac{l^2}{L}\) |
Two coils have a mutual inductance of \(5\) mH. The current changes in the first coil according to the equation \(I=I_{0}\cos\omega t,\) where \(I_{0}=10~\text{A}\) and \(\omega = 100\pi ~\text{rad/s}\). The maximum value of emf induced in the second coil is:
1. \(5\pi~\text{V}\)
2. \(2\pi~\text{V}\)
3. \(4\pi~\text{V}\)
4. \(\pi~\text{V}\)
1. | \(5\) H | 2. | \(2.5\) H |
3. | \(1.5\) H | 4. | \(2\) H |
Eddy currents are used in:
1. Induction furnace
2. Electromagnetic brakes
3. Speedometers
4. All of these
A short magnet is allowed to fall along the axis of a horizontal metallic ring. Starting from rest, the distance fallen by the magnet in one second may be:
1. | \(4\) m | 2. | \(5\) m |
3. | \(6\) m | 4. | \(7\) m |