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:

1.	100 J	2.	60 J
3.	80 J	4.	120 J

A wire of length 6 m is rotated about the axis passing through point C and parallel to the magnetic field lines with angular velocity 4 radian/second. If B = 0.5T, the potential difference across the ends of the wire is

1. 2 V

2. 6 V

3. 12 V

4. Zero

The current flowing in an inductor of inductance 2.0 H varies as i = 2 sin(40t + $\pi /3$), where i is in amperes and t is in seconds. The maximum value of the emf induced in the inductor is:

1. 320 V

2. 160 V

3. 80 V

4. 4 V

If a magnet is allowed to fall through a long conducting pipe, then the final acceleration of the magnet will be

1. = g

2. $>g$

3. Zero

4. $\ge g$

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:

Which of the following is not based on the application of eddy currents?

1. Speedometer

2. Dead-beat galvanometer

3. Energy meter

4. Tangent galvanometer

A railway track running north-south has two parallel rails l distance apart. If H is the horizontal component of the earth's field, angle of dip is $\theta$, then the induced emf between the rails when a train passes with velocity v, is

1. Hlvtan$\theta$

2. Hlv

3. Hlvcos$\theta$

4. Hlvsin$\theta$

Two coils of self-inductance L₁ and L₂ are placed so close together that they completely link the magnetic flux of each other. If M be their mutual inductance then, the correct relation is 

1. M = $\sqrt{\frac{L_1}{L_2}}$

2. M = L₁$\sqrt{L_2}$

3. M = L₁L₂

4. M = $\sqrt{L_1{L}_2}$

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

Two discs of radii R and 2R are moving with velocities v and 2v in opposite directions on a conducting platform, as shown in the figure. If magnetic field B is applied in the plane perpendicular to the discs, then the potential difference between two points P and Q which are the topmost points of the discs is 

1. 8BRv

2. 4BRv

3. 10BRv

4. 2BRv