Electromagnetic Induction · Question 22

A thin semicircular conducting ring (PQR) of radius r is falling with its plane vertical in a horizontal magnetic field B, as shown in the figure. [figure] The potential difference developed across the ring when its speed is v, is

1. zero
2. Bv r22 and P is at higher potential
3. rBv and R is at higher potential
4. 2rBv and R is at higher potential

A wire loop is rotated in a magnetic field. The frequency of change of direction of the induced e.m.f. is

1. four times per revolution
2. six times per revolution
3. once per revolution
4. twice per revolution

A current of 2.5 A flows through a coil of inductance 5 H. The magnetic flux linked with the coil is

1. 0.5 Wb
2. 12.5 Wb
3. zero
4. 2 Wb

In a coil of resistance 10 , the induced current developed by changing magnetic flux through it, is shown in figure as a function of time. The magnitude of change in flux through the coil in weber is [figure]

1. 8
2. 2
3. 6
4. 4

A coil of resistance 400 is placed in a magnetic field. If the magnetic flux (Wb) linked with the coil varies with time t (sec) as = 50t2 + 4. The current in the coil at t = 2 sec is

1. 0.5 A
2. 0.1 A
3. 2 A
4. 1 A

The current (I) in the inductance is varying with time according to the plot shown in figure. [figure] Which one of the following is the correct variation of voltage with time in the coil ?

1. [figure]
2. [figure]
3. [figure]
4. [figure]

The current i in a coil varies with time as shown in the figure. The variation of induced emf with time would be [figure]

1. [figure]
2. [figure]
3. [figure]
4. [figure]

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

1. 2
3. 2
4. 2

A rectangular, a square, a circular and an elliptical loop, all in the (x-y) plane, are moving out of a uniform magnetic field with a constant velocity V = v i. The magnetic field is directed along the negative z axis direction. The induced emf, during the passage of these loops, out of the field region, will not remain constant for

1. the circular and the elliptical loops
2. only the elliptical loop
3. any of the four loops
4. the rectangular, circular and elliptical loops

A conducting circular loop is placed in a uniform magnetic field 0.04 T with its plane perpendicular to the magnetic field. The radius of the loop starts shrinking at 2 mm/s. The induced emf in the loop when the radius is 2 cm is

1. 4.8 V
2. 0.8 V
3. 1.6 V
4. 3.2 V