A square metallic wire loop of side 0.1 m and resistance of \(1~\Omega\) is moved with a constant velocity in a magnetic field of \(2~\mathrm{wb/m^2}\) as shown in the figure. The magnetic field is perpendicular to the plane of the loop and the loop is connected to a network of resistances. What should be the velocity of the loop so as to have a steady current of 1 mA in the loop?

   

1.	1 cm/sec	2.	2 cm/sec
3.	3 cm/sec	4.	4 cm/sec

A conductor ABOCD moves along its bisector with a velocity of 1 m/s through a perpendicular magnetic field of 1 wb/m², as shown in fig. If all the four sides are of 1m length each, then the induced emf between points A and D is

(1) 0

(2) 1.41 volt

(3) 0.71 volt

(4) None of the above

A conducting rod PQ of length L = 1.0 m is moving with a uniform speed v = 2 m/s in a uniform magnetic field B = 4.0 T directed into the paper. A capacitor of capacity C = 10 μF is connected as shown in figure. Then

(1) q_A = + 80 μC and q_B = – 80 μC

(2) q_A = – 80 μC and q_B = + 80 μC

(3) q_A = 0 = q_B

(4) Charge stored in the capacitor increases exponentially with time

The resistance in the following circuit is increased at a particular instant. At this instant the value of resistance is 10 Ω. The current in the circuit will be:

1. i = 0.5 A

2. i > 0.5 A

3. i < 0.5 A

4. i = 0

Shown in the figure is a circular loop of radius r and resistance R. A variable magnetic field of induction B = B₀e^–t is established inside the coil. If the key (K) is closed, the electrical power developed right after closing the switch, at t=0, is equal to

(1) $\frac{B_0^2\pi r^2}{R}$

(2) $\frac{B_{0}10r^3}{R}$

(3) $\frac{B_0^2{\pi }^2{r}^{4}R}{5}$

(4) $\frac{B_0^2{\pi }^2{r}^4}{R}$

A highly conducting ring of radius R is perpendicular to and concentric with the axis of a long solenoid as shown in fig. The ring has a narrow gap of width d in its circumference. The solenoid has a cross-sectional area A and a uniform internal field of magnitude B₀. Now beginning at t = 0, the solenoid current is steadily increased so that the field magnitude at any time t is given by B(t) = B₀ + αt where α > 0. Assuming that no charge can flow across the gap, the end of the ring which has an excess of positive charge and the magnitude of induced e.m.f. in the ring are respectively

(1) X, Aα

(2) X πR²α

(3) Y, πA²α

(4) Y, πR²α

A rectangular loop with a sliding connector of length l = 1.0 m is situated in a uniform magnetic field B = 2 T perpendicular to the plane of the loop. Resistance of connector is r = 2 Ω. Two resistances of 6 Ω and 3 Ω are connected as shown in the figure. The external force required to keep the connector moving with a constant velocity v = 2 m/s is:

A wire cd of length l and mass m is sliding without friction on conducting rails ax and by as shown. The vertical rails are connected to each other with a resistance R between a and b. A uniform magnetic field B is applied perpendicular to the plane abcd such that cd moves with a constant velocity of

(1) $\frac{mgR}{Bl}$

(2) $\frac{mgR}{B^2{l}^2}$

(3) $\frac{mgR}{B^3{l}^3}$

(4) $\frac{mgR}{B^{2}l}$

A conducting rod AC of length 4l is rotated about a point O in a uniform magnetic field $\overrightarrow{B}$ directed into the paper. AO = l and OC = 3l. Then

(1) $V_A-V_O=\frac{B\omega l^2}{2}$

(2) $V_O-V_C=\frac{7}{2}B\omega l^2$

(3) $V_A-V_C=4B\omega l^2$

(4) $V_C-V_O=\frac{9}{2}B\omega l^2$

The figure shows three circuits with identical batteries, inductors, and resistors. Rank the circuits according to the current, in descending order, through the battery (i) just after the switch is closed and (ii) a long time later: