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 coil is wound of a frame of rectangular cross-section. If the linear dimensions of the frame are doubled and the number of turns per unit length of the coil remains the same, then the self inductance increases by a factor of:
1. | \(6\) | 2. | \(12\) |
3. | \(8\) | 4. | \(16\) |
A conducting circular loop is placed in a uniform magnetic field of \(0.04\) T with its plane perpendicular to the magnetic field. The radius of the loop starts shrinking at a rate of \(2\) mm/s. The induced emf in the loop when the radius is \(2\) cm is:
1. \(3.2\pi ~\mu \text{V}\)
2. \(4.8\pi ~\mu\text{V}\)
3. \(0.8\pi ~\mu \text{V}\)
4. \(1.6\pi ~\mu \text{V}\)
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. |
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 |
1. | \(5\) | 2. | \(10\) |
3. | \(15\) | 4. | \(20\) |
The current in a coil varies with time \(t\) as \(I= 3 t^{2} +2t\). If the inductance of coil be \(10\) mH, the value of induced emf at \(t=2~\text{s}\) will be:
1. \(0.14~\text{V}\)
2. \(0.12~\text{V}\)
3. \(0.11~\text{V}\)
4. \(0.13~\text{V}\)
1. | \(0.04\) V | 2. | \(0.4\) V |
3. | \(4\) V | 4. | \(0.004\) V |
The network shown in figure is a part of a complete circuit. If at a certain instant, the current \(i\) is \(10\) A and is increasing at the rate of \(4\times 10^{3}\) A/sec, then \(V_A-V_B\) is:
1. | \(6\) V | 2. | \(-6\) V |
3. | \(10\) V | 4. | \(-10\) V |
The back emf induced in a coil, when current changes from \(1\) ampere to zero in one milli-second, is \(4\) volts. The self-inductance of the coil is:
1. \(1~\text{H}\)
2. \(4~\text{H}\)
3. \(10^{-3}~\text{H}\)
4. \(4\times10^{-3}~\text{H}\)