Two rails of a railway track insulated from each other on the ground are connected to a millivoltmeter. The reading of millivoltmeter when the train travels at a speed of 20m/s along the track is (Given: B_v = 0.2$\times$10^-4 Wb/m² and distance between the rails is 1m)

1. 10 mV

2. 0.4 mV

3. 40 mV

4. 4 mV

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 into a magnetic field with a constant velocity \(v,\) as shown in the figure. The front edge of the loop enters the magnetic field at \(t=0.\) Which of the following graphs correctly represents the variation of the induced EMF, \(E\) in the loop over time \(t,\) given its constant velocity in the magnetic field?
(consider anticlockwise current as negative and clockwise current as positive)

1.		2.
3.		4.

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$\propto \frac{1}{{\mathrm{l}}^2}$