A copper rod of mass m slides under gravity on two smooth parallel rails l distance apart and set at an angle to the horizontal as shown in fig. At the bottom, the rails are joined by a resistance R. There is a uniform magnetic field perpendicular to the plane of the rails. The terminal velocity of the rod is:
1.
2.
3.
4.
A square coil ACDE with its plane vertical is released from rest in a horizontal uniform magnetic field of length 2L (figure). The acceleration of the coil is:
1. | less than g for all the time till the loop crosses the magnetic field completely. |
2. | less than g when it enters the field and greater than g when it comes out of the field. |
3. | g all the time. |
4. | less than g when it enters and comes out of the field but equal to g when it is within the field. |
Two coils of 10 turns each are arranged such that the mutual inductance between them is 150 mH. The magnetic flux linked through one coil when 2 amperes current will flow in another coil, will be:
1.
2.
3.
4.
A 10 H inductor carries a current of 20 A. How much ice at 0°C could be melted by the energy stored in the magnetic field of the inductor?
Latent heat of ice is 2.26 × J/kg .
1. | 0.08 kg | 2. | 8.8 kg |
3. | 0.88 kg | 4. | 0.44 kg |
Some magnetic flux is changed from a coil of resistance 10 . As a result, an induced current is developed in it, which varies with time as shown in the figure. The magnitude of change in flux through the coil in Wb is:
1. | 2 | 2. | 4 |
3. | 6 | 4. | None of these |
When the current in the portion of the circuit shown in the figure is 2 A and increases at the rate of 1 A/s, the measured potential difference 8 V. However, when the current is 2 A and decreases at the rate of 1 A/s, the measured potential difference 4 V. The value of R and L is:
1. | 3 Ω and 2 H respectively |
2. | 3 Ω and 3 H respectively |
3. | 2 Ω and 1 H respectively |
4. | 3 Ω and 1 H respectively |
In the circuit diagram shown in figure, R = 10 \(\Omega\), L = 5 H, E = 20 V and i = 2 A. This current is decreasing at a rate of 1.0 A/s. at this instant will be:
1. | 40 V | 2. | 35 V |
3. | 30 V | 4. | 45 V |
A straight solenoid has 50 turns per cm in primary coil and 200 turns in the secondary coil. The area of cross-section of the solenoid is 4 cm2. Calculate the mutual inductance.
1. 5.0 H
2.
3. 2.5 H
4.
A \(1~\text{m}\) long metallic rod is rotating with an angular frequency of \(400~\text{rad/s}\) about an axis normal to the rod passing through its one end. The other end of the rod is in contact with a circular metallic ring. A constant and uniform magnetic field of \(0.5~\text{T}\) parallel to the axis exists everywhere. The emf induced between the center and the ring is:
1. \(200~\text{V}\)
2. \(100~\text{V}\)
3. \(50~\text{V}\)
4. \(150~\text{V}\)
A horizontal straight wire 10 m long extending from east to west is falling with a speed of 5.0 ms-1 at right angle to the horizontal component of the earth's magnetic field, \(0.30 \times 10^{-4} \mathrm{~Wb} \mathrm{~m}^{-2}\)
. The instantaneous value of the emf induced in the wire is:
1. | \(2.5 \times 10^{-3} V\) |
2. | \(1.5 \times 10^{-4} V\) |
3. | \(2.5 \times 10^{-4} V\) |
4. | \(1.5 \times 10^{-3} V\) |