A conducting circular loop is placed in a uniform magnetic field, B= 0.025 T with its plane perpendicular to the loop.The radius of the loop is made to shrink at a constant rate of 1 mm s^–1. The induced e.m.f. when the radius is 2 cm, is

2πμV
πμV
^π⁄₂μV
2μV

Solution

The magnetic flux through a circuit of resistance R changes by an amount Δ φ in a time Δt. Then the total quantity of electric charge Q that passes any point in the circuit during the time Δt is represented b

\(Q=R\frac{\Delta \phi }{\Delta t}\)
\(Q=\frac{1}{R}\frac{\Delta \phi }{\Delta t}\)
\(Q=\frac{1}{R}\frac{\Delta \phi }{\Delta t}\)
\(Q=\frac{\Delta \phi }{\Delta t}\)

Solution

In an inductor of self-inductance L = 2 mH, current changes with time according to relation i= t²e^–t. At what time emf is zero?

Solution

A varying current in a coil change from 10A to zero in 0.5 sec. If the average e.m.f induced in the coil is 220V, the self-inductance of the coil is

5 H
6 H
11 H
12 H

Solution

Two coaxial solenoids are made by winding thin insulated wire over a pipe of cross-sectional are aA = 10 cm² and length = 20 cm. If one of the solenoid has 300 turns and the other 400 turns, their mutual inductance is(μ₀= 4π × 10 ^–7 Tm A^–1)

2.4π × 10^–5 H
4.8π × 10^–4 H
4.8π × 10^–5 H
2.4π × 10^–4 H

Solution

A solenoid has 2000 turns wound over a length of 0.3 m. Its cross-sectional area is 1.2 × 10^-3 m². Around its central section a coil of 300 turns is wound. If an initial current of 2 A flowing in the solenoid is reversed in 0.25 s,the emf induced in the coil will be

2.4 × 10^-4 V
2.4 × 10^-2 V
4.8 ×10^-4 V
4.8 × 10^-2 V

Solution

In a circuit given in figure 1 and 2 are ammeters. Just after key K is pressed to complete the circuit, the reading is

zero in both 1 and 2
maximum in both 1 and 2
zero in 1 and maximum in 2
maximum in 1 and zero in 2

Solution

Capacitor is a dc blocking element and hence no current flow in (1).
An inductor offers a zero resistance path to flow of dc and hence maximum current flows through (2).

In fig., final value of current in 10Ω resistor, when plug of key K is inserted is

\(\frac{3}{10}A\)
\(\frac{3}{20}A\)
\(\frac{3}{11}A\)
zero

Solution

As resistance of 1 H coil is zero, the entire current flows through the coil. Current through 10Ω resistance is zero.

A square loop of side a is rotating about its diagonal with angular velocity ω in a perpendicular magnetic field \(\overrightarrow{B}\). It has 10 turns. The emf induced is

B a² sin ωt
B a² cos ωt
5 √2 B a²
10 B a² sin ωt

Solution

Two identical circular loops of metal wire are lying on a table without touching each other.Loop A carries a current which increases with time. In response the loop B

remains stationary
is attracted by loop A
is repelled by loop A
rotates about is CM with CM fixed

Solution

An opposite current induced in B in accordance to Lenz's law. So the two loops repel each other.

UnAttempted

0

Attempted

0

Correct

0

Wrong

0

Complete