(a) | use more turns of wire in the coil. |
(b) | use thicker wire. |
(c) | change the speed of rotation. |
1. | (c) only |
2. | (a), (b) and (c) |
3. | (a) and (b) only |
4. | (a) and (c) only |
The core of a transformer is laminated because:
1. | Energy losses due to eddy currents may be minimized |
2. | The weight of the transformer may be reduced |
3. | Rusting of the core may be prevented |
4. | Ratio of voltage in primary and secondary may be increased |
1. | \(\frac{\varepsilon^{2} R}{\left[R^{2}+\left(L \omega-\frac{1}{C \omega}\right)^{2}\right]}\) | 2. | \(\frac{\varepsilon^{2} \sqrt{R^{2}+\left(L \omega-\frac{1}{C \omega}\right)^{2}}}{R}\) |
3. | \(\frac{\varepsilon^{2}\left[R^{2}+\left(L \omega-\frac{1}{C \omega}\right)^{2}\right]}{R}\) | 4. | \(\frac{\varepsilon^{2}R}{\sqrt{R^{2}+\left(L \omega-\frac{1}{C \omega}\right)^{2}}}\) |
A coil of inductive reactance of \(31~\Omega\) has a resistance of \(8~\Omega\). It is placed in series with a condenser of capacitive reactance \(25~\Omega\). The combination is connected to an AC source of \(110\) V. The power factor of the circuit is:
1. \(0.56\)
2. \(0.64\)
3. \(0.80\)
4. \(0.33\)
1. | When the capacitor is air-filled. |
2. | When the capacitor is mica filled. |
If the current through the resistor is \(I\) and the voltage across the capacitor is \(V\), then:
1. \(V_a < V_b\)
2. \(V_a > V_b\)
3. \(i_a > i_b\)
4. \(V_a = V_b\)
Consider now the following statements
I. | Readings in \(A\) and \(V_2\) are always in phase |
II. | Reading in \(V_1\) is ahead in phase with reading in \(V_2\) |
III. | Readings in \(A\) and \(V_1\) are always in phase |
1. | I only | 2. | II only |
3. | I and II only | 4. | II and III only |
The figure shows the variation of \(R\), \(X_L\), and \(X_C\) with frequency \(f\) in a series of \(L\), \(C\), and \(R\) circuits. For which frequency point is the circuit inductive?
1. | \(A\) | 2. | \(B\) |
3. | \(C\) | 4. | All points |