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. \(8~\text{V}\)
An inductor coil of self-inductance \(10~\mathrm H\) carries a current of \(1~\mathrm A\) . The magnetic field energy stored in the coil is:
1. | \(10~\mathrm J\) | 2. | \(2.5~\mathrm J\) |
3. | \(20~\mathrm J\) | 4. | \(5~\mathrm J\) |