A uniform magnetic field is restricted within a region of radius \(r\). The magnetic field changes with time at a rate \(\frac{dB}{dt}\). Loop \(1\) of radius \(R>r\) is enclosed within the region \(r\) and loop \(2\) of radius \(R\) is outside the region of the magnetic field as shown in the figure. Then, the emf generated is:
1. | \(1\) and zero in loop \(2\) | zero in loop
2. | \(-\frac{dB}{dt}\pi r^2\) in loop \(1\) and zero in loop \(2\) |
3. | \(-\frac{dB}{dt}\pi R^2\) in loop \(1\) and zero in loop \(2\) |
4. | \(1\) and not defined in loop \(2\) | zero in loop
An electron moves on a straight-line path \(XY\) as shown. The \(\mathrm{abcd}\) is a coil adjacent to the path of electrons. What will be the direction of current if any, induced in the coil?
1. | \(\mathrm{abcd}\) |
2. | \(\mathrm{adcb}\) |
3. | The current will reverse its direction as the electron goes past the coil |
4. | No current included |
A conducting square frame of side \(a\) and a long straight wire carrying current \(I\) are located in the same plane as shown in the figure. The frame moves to the right with a constant velocity \(v.\) The emf induced in the frame will be proportional to:
A thin semicircular conducting the ring \((PQR)\) of radius \(r\) is falling with its plane vertical in a horizontal magnetic field \(B,\) as shown in the figure. The potential difference developed across the ring when it moves with speed \(v\) is:
1. | zero |
2. | \(Bv\pi r^{2}/2\) and \(P\) is at a higher potential |
3. | \(\pi rvB\) and \(R\) is at a higher potential |
4. | \(2BvR\) and \(R\) is at higher potential |
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. |
1. | twice per revolution. |
2. | four times per revolution. |
3. | six times per revolution. |
4. | once per revolution. |
A coil of resistance \(400~\Omega\) is placed in a magnetic field. The magnetic flux \(\phi~\text{(Wb)}\) linked with the coil varies with time \(t~\text{(s)}\) as \(\phi=50t^{2}+4.\) The current in the coil at \(t=2~\text{s}\) is:
1. \(0.5~\text{A}\)
2. \(0.1~\text{A}\)
3. \(2~\text{A}\)
4. \(1~\text{A}\)
The current (\(I\)) in the inductance is varying with time (\(t\)) according to the plot shown in the figure.
1. | ![]() |
2. | ![]() |
3. | ![]() |
4. | ![]() |
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. |