The current through a choke coil increases from zero to 6 A in 0.3 seconds and an induced emf of 30 V is produced. The inductance of the coil is:

1.	5 H	2.	2.5 H
3.	1.5 H	4.	2 H

Self-inductance of primary and secondary of a perfectly coupled coil is 40 mH and 90mH respectively. Coefficient of mutual induction between them is

1. 65 mH

2. 50 mH

3. 130 mH

4. 60 mH

A conducting square loop of side L and resistance R moves in its plane with a uniform velocity v perpendicular to one of its sides. A constant magnetic field B exists as shown in the figure. Mechanical power required to maintain its uniform velocity is

1. $\frac{B^2{L}^2{v}^2}{R}$

2. $\frac{B^2{L}^2{v}^2}{2R}$

3. $\frac{B^2{L}^2{v}^2}{4R}$

4. Zero

A conducting disc of radius r rotates about its axis with an angular speed $\omega$ in a uniform magnetic field B perpendicular to the plane of the disc as shown. A resistance R is connected between centre and rim of the disc, then-

1. No e.m.f. will induce across the resistance

2. E.m.f. will induce and A is at high potential

3. Current in resistance will flow from A to B

4. Resistance becomes hot due to Joule's heating

A train is moving on a straight horizontal track. Induced emf across the axle is maximum when it moves

1. At poles

2. At equator

3. Along the direction where the angle of dip is 45$°$

4. Emf is not induced

A square loop enters a magnetic field with velocity v as shown in the figure. The front edge enters the magnetic field at time t = 0. Which of the following graphs gives the correct variation of emf$\epsilon$ induced in the loop with time t for its constant velocity in the magnetic field? [Take anticlockwise current as negative and vice versa]

A rectangular metal loop ABCD of is passed through the magnetic field with a constant velocity v. Which of the following represents power (P) dissipated vs time (t) graph?

1.                2. 
3.                4. 

Self-inductance of a solenoid is 5 mH. If the current is decreasing through it at the rate 10⁺³ A/s, then emf induced in the solenoid is

1. -5V

2. 5V

3. 2.5V

4. -2.5V

Keeping number of turns constant self inductance L of a solenoid varies with its length l as

1. L$\propto$l

2. L$\propto \frac{1}{\mathrm{l}}$

3. L$\propto {\mathrm{l}}^2$

4. L$\propto \frac{1}{{\mathrm{l}}^2}$

A conducting rod AC of length 4l is rotated with angular velocity $\omega$ about a point O in a uniform magnetic field $\overrightarrow{B}$ directed into the plane of the paper. If AO = l and OC = 3l, then the potential difference between A and C, V_A - V_C is

1. $2{\mathrm{B\omega l}}^2$

2. ${\mathrm{B\omega l}}^2$

3. $3{\mathrm{B\omega l}}^2$

4. $4{\mathrm{B\omega l}}^2$