A long solenoid has \(1000\) turns. When a current of \(4\) A flows through it, the magnetic flux linked with each turn of the solenoid is \(4\times 10^{-3}\) Wb. The self-inductance of the solenoid is:
1. \(3\) H
2. \(2\) H
3. \(1\) H
4. \(4\) H
A wire loop is rotated in a magnetic field. The frequency of change of direction of the induced e.m.f. is:
1. | Twice per revolution | 2. | Four times per revolution |
3. | Six times per revolution | 4. | Once per revolution |
The current \(i\) in an inductance coil varies with time \(t\) according to the graph shown in the figure. Which one of the following plots shows the variation of voltage in the coil with time?
1. | 2. | ||
3. | 4. |
A bar magnet is released along the vertical axis of the conducting coil. The acceleration of the bar magnet is:
1. | greater than \(g\). | 2. | less than \(g\). |
3. | equal to \(g\). | 4. | zero. |
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. \(\frac{B l v}{\frac{1}{R_{1}} + \frac{1}{R_{2}} + \frac{1}{R_{0}}}\)
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. \(\pi~\text{V}\)
Eddy currents are used in:
1. Induction furnace
2. Electromagnetic brakes
3. Speedometers
4. All of these