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

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

1. Zero

2. $Bv{\mathrm{\pi r}}^2/2$ and P is at the higher potential

3. $\mathrm{\pi rBv}$ and R is at the higher potential

4. 2BvR and R is at the higher potential

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

1. 0.5 A

2. 0.1 A

3. 2 A

4. 1 A

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

1.  

2.  

3.  

4.  

Two coils of self-inductance 2 mH and 8 mH are placed so close together that the effective flux in one coil is completely linked with the other. The mutual inductance between these coils is:

1. 10 mH

2. 6 mH

3. 4 mH

4. 16 mH

In which of the following devices, the eddy current effect is not used?

1. electric heater

2. induction furnace

3. magnetic braking in train

4. electromagnet

A 800 turn coil of effective area 0.05 $m^2$ is kept perpendicular to a magnetic field $5\times {10}^{-5} T$. When the plane of the coil is rotated by 90$°$ around any of its coplanar axis in 0.1 s, the emf induced in the coil will be:

1. 0.02V

2. 2 V

3. 0.2 V

4. $2\times {10}^{-3} V$

A cycle wheel of radius 0.5 m is rotated with a constant angular velocity of 10 rad/s in a region of a magnetic field of 0.1 T which is perpendicular to the plane of the wheel. The EMF generated between its centre and the rim is:

(1) 0.25 V

(2) 0.125 V

(3) 0.5 V

(4) zero

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 mms^-1. The induced emf when the radius is 2 cm is:

1. 2$\pi \mu$V

2. $\pi \mu$V

3. $\frac{\pi }{2}\mu V$

4. 2$\mu$V

An electron moves on a straight-line path XY as shown. The abcd is a coil adjacent to the path of electrons. What will be the direction of current if any, induced in the coil? 
,

1. abcd

2. adcb

3. The current will reverse its direction as the electron goes past the coil

4. No current included