Q. No.A circular disc of radius 0.2 m is placed in a uniform magnetic field of induction in such a way that its axis makes an angle of with .
The magnetic flux linked to the disc will be:
1. 0.02 Wb
2. 0.06 Wb
3. 0.08 Wb
4. 0.01 Wb
1. 0.02 Wb
2. 0.06 Wb
3. 0.08 Wb
4. 0.01 Wb
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:
| 1. | \((i) i_2>i_3>i_1\left(i_1=0\right) (ii) i_2>i_3>i_1\) |
| 2. | \((i) i_2<i_3<i_1\left(i_1 \neq 0\right) (ii) i_2>i_3>i_1\) |
| 3. | \((i) i_2=i_3=i_1\left(i_1=0\right)\left(\right. (ii) i_2<i_3<i_1\) |
| 4. | \((i) i_2=i_3>i_1\left(i_1 \neq 0\right) (ii) i_2>i_3>i_1\) |
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
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 thin semicircular conducting ring of radius R is falling with its plane vertical in a horizontal magnetic induction B. At the position MNQ, the speed of the ring is v and the potential difference developed across the ring is:
| 1. | Zero |
| 2. | \(B v \pi R^2 / 2\) and M is at the higher potential |
| 3. | \(2 R B v\) and M is at the higher potential |
| 4. | \(2RBv\) and Q is at the higher potential |
A metallic ring is attached to the wall of a room. When the north pole of a magnet is brought near to it, the induced current in the ring will be:
| 1. | first clockwise and then anticlockwise. |
| 2. | in the clockwise direction. |
| 3. | in the anticlockwise direction. |
| 4. | first anticlockwise and then clockwise. |
The key K is inserted at time t= 0. The initial (t=0) and final currents through the battery are:
1. \(\frac{1}{15}~A,~\frac{1}{10}~A\)
2. \(\frac{1}{10}~A,~\frac{1}{15}~A\)
3. \(\frac{2}{15}~A,~\frac{1}{10}~A\)
4. \(\frac{1}{15}~A,~\frac{2}{25}~A\)
A coil of self-inductance \(L\) is connected in series with a bulb \(\mathrm{B}\) and an AC source. The brightness of the bulb decreases when:
| 1. | number of turns in the coil is reduced. |
| 2. | a capacitance of reactance \(X_C = X_L\) is included in the same circuit. |
| 3. | an iron rod is inserted in the coil. |
| 4. | frequency of the AC source is decreased. |
| I: | A small magnet takes a longer time in falling into a hollow metallic tube without touching the wall. |
| II: | There is an opposition to motion due to the production of eddy currents in a metallic tube. |
Choose the correct option for the above statements:
| 1. | Both I and II are true and II is the correct explanation for I. |
| 2. | Both I and II are true and II is not the correct explanation for I. |
| 3. | I is true but II is false. |
| 4. | I is false but II is true. |
An aeroplane in which the distance between the tips of wings is 50 m is flying horizontally with a speed of 360 km/hr over a place where the vertical component of earth magnetic field is . The potential difference between the tips of wings would be:
| 1. | 0.1 V | 2. | 1.0 V |
| 3. | 0.2 V | 4. | 0.01 V |
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