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.	\(13.89~\text H\)

A conducting square frame of side \(a\) and a long straight wire carrying current \(I\) are located in the same plane as shown in the figure. The frame moves to the right with a constant velocity \(v.\) The emf induced in the frame will be proportional to:

As a result of change in the magnetic flux linked to the closed loop shown in the figure, an e.m.f. V volt is induced in the loop. The work done (joules) in taking a charge Q coulomb once along the loop is-

1.  QV

2.  QV/2

3.  2QV

4.  Zero 

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.

The current \(i\) in a coil varies with time as shown in the figure. The variation of induced emf with time would be:
     

1.		2.
3.		4.

Two coils of self-inductance \(2~\text{mH}\) and \(8~\text{mH}\) are placed so close together that the effective flux in one coil is completely linked with the other. The mutual inductance between these coils is:
1. \(10~\text{mH}\)
2. \(6~\text{mH}\)
3. \(4~\text{mH}\)
4. \(16~\text{mH}\)

In which of the following devices, the eddy current effect is not used?
1. Electric heater
2. Induction furnace
3. Magnetic braking in train
4. Electromagnet