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

A coil has 500 turns and the flux through the coil is \(\phi=3t^{2} +4t+9\) milliweber. The magnitude of induced emf between the ends of the coil at t = 5 s is:

1. 34 millivolt

2. 17 volt

3. 17 millivolt

4. 34 volt

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:

Work done in increasing the current through a solenoid from 0 to 2 A is 20 J. Work done in increasing the current from 4 A to 6 A is:

In a uniform magnetic field, a ring is rotating about its axis which is parallel to the magnetic field and the magnetic field is perpendicular to the plane of the ring. The induced electric field in the ring:

Calculate the self-inductance of a solenoid having 1000 turns and length 1 m. The area of cross-section is 7 cm² and \(\mu_r=1000\)

1. 888 H

2. 0.88 H

3. 0.088 H

4. 88.8 H

A rod having length l and resistance R₀ is moving with speed v as shown in the figure. The current through the rod is:
               
1. $\frac{Blv}{{\displaystyle \frac{R_1{R}_2}{R_1+R_2}}+R_0}$

2. $\frac{\mathrm{Blv}}{{\left({\displaystyle \frac{1}{{\mathrm{R}}_1}}+{\displaystyle \frac{1}{{\mathrm{R}}_2}}+{\displaystyle \frac{1}{{\mathrm{R}}_{\mathrm{o}}}}\right)}^2}$

3. $\frac{Blv}{R_1+R_2+R_0}$

4. $\frac{Blv}{{\displaystyle \frac{1}{R_1}}+{\displaystyle \frac{1}{R_2}}+{\displaystyle \frac{1}{R_0}}}$

A solenoid of inductance L and resistance R is connected to a battery of e.m.f. E. Maximum value of magnetic energy stored in the inductor is:

$1.$ $\frac{E^2}{2R}$
$2.$ $\frac{E^{2}L}{2R^2}$
$3.$ $\frac{E^{2}L}{R}$ $$
$4.$ $\frac{E^{2}L}{2R}$

The coefficient of mutual inductance between two coils depends upon: