Q. No.1. \(1:2\)
2. \(2:1\)
3. \(8:1\)
4. \(1:8\)
1. \(8~\mu \text{J}\)
2. \(4~\mu \text{J}\)
3. \(4~\text{mJ}\)
4. \(8~\text{mJ}\)
The current in an inductor of self-inductance \(4~\text{H}\) changes from \(4~ \text{A}\) to \(2~\text{A}\) in \(1~ \text s\). The emf induced in the coil is:
1. \(-2~\text{V}\)
2. \(2~\text{V}\)
3. \(-4~\text{V}\)
4. \(8~\text{V}\)
| 1. | \(10~\text{J}\) | 2. | \(2.5~\text{J}\) |
| 3. | \(20~\text{J}\) | 4. | \(5~\text{J}\) |
The magnetic potential energy stored in a certain inductor is \(25~\text{mJ},\) when the current in the inductor is \(60~\text{mA}.\) This inductor is of inductance:
1. \(0.138~\text H\)
2. \(138.88~\text H\)
3. \(1.389~\text H\)
4. \(13.89~\text H\)
| 1. | number of turns in the coil is reduced. |
| 2. | a capacitance of reactance \(X_C = X_L\) is included in the same circuit. |
| 3. | an iron rod is inserted in the coil. |
| 4. | frequency of the AC source is decreased. |
The current \((I)\) in the inductance is varying with time \((t)\) according to the plot shown in the figure.
Which one of the following is the correct variation of voltage with time in the coil?
| 1. |  |
2. |  |
| 3. |  |
4. |  |
1. \(2.5 ~\text{H}\)
2. \(2.0 ~\text{H}\)
3. \(1.0 ~\text{H}\)
4. \(4.0 ~\text{H}\)
For a coil having \(L=2~\text{mH},\) the current flow through it is \(I=t^2e^{-t}.\) The time at which emf becomes zero is:
1. \(2\) s
2. \(1\) s
3. \(4\) s
4. \(3\) s
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