The current passing through a choke coil of 5 H is decreasing at the rate of 3 As^-1. The emf induced in the coil is 

1. 15 V

2. -15 V

3. $\frac{5}{3}V$

4. $\frac{-5}{3}V$

If all linear dimensions of an inductor are tripled, then self-inductance will become (keeping the total number of turns per unit length constant)

1.  3 times

2.  9 times

3.  27 times

4. 1/3 times

A coil of resistance 20 $\Omega$ and inductance 5 H has been connected to a 200 V battery. The maximum energy stored in the coil is:

Two coils have a mutual inductance of 5 mH. Current changes in the first coil according to the equation I = $I_0$cos wt, where $I_0$ = 10 A and $\mathrm{\omega } = 100\mathrm{\pi }$ rad/s. Maximum value of e.m.f. induced in the second coil is

1.  5$\pi$ volt

2.   2$\pi$ volt

3.  4$\pi$ volt

4.  $\pi$ volt

Lenz's law is a consequence of the law of conservation of 

(1) Charge

(2) Momentum

(3) Mass

(4) Energy

A copper ring is held horizontally and a bar magnet is dropped through the ring with its length along the axis of the ring. The acceleration of the falling magnet while it is passing through the ring is

(1) Equal to that due to gravity

(2) Less than that due to gravity

(3) More than that due to gravity

(4) Depends on the diameter of the ring and the length of the magnet

A magnet is brought towards a coil first (i) speedily (ii) slowly. It can be concluded that the induced e.m.f. and the induced charge in the two cases, will be respectively:

As shown in the figure, a magnet is moved at a fast speed towards a coil at rest. Due to this induced electromotive force, induced current and induced charge in the coil is E, I, and Q respectively. If the speed of the magnet is doubled, the incorrect statement is:

The magnetic field in a coil of 100 turns and 40 square cm area is increased from 1 Tesla to 6 Tesla in 2 second. The magnetic field is perpendicular to the coil. The e.m.f. generated in it is 

(1) 10⁴ V

(2) 1.2 V

(3) 1.0 V

(4) 10^–2 V

A metallic ring connected to a rod oscillates freely like a pendulum. If now a magnetic field is applied in the horizontal direction so that the pendulum now swings through the field, the pendulum will: