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. | \(13.89~\text H\) |