Q. No.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. \(3.6\) A
2. \(2.8\) A
3. \(2.5\) A
4. \(5.0\) A
| 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. \(V_a = V_b\)
\(1 .\) \(P \left(\frac{R}{Z}\right)^{2}\)
\(2 .\) \(P \sqrt{\frac{R}{Z}}\)
\(3 .\) \(P \left(\frac{R}{Z}\right)\)
\(4 .\) \(P\)
| 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 |
(\(f= 50~\text{Hz}\))
| 1. | \(0.052\) H | 2. | \(2.42\) H |
| 3. | \(16.2\) mH | 4. | \(1.62\) mH |
In an \(LCR\) series network, \(V_L = 40~\text{V}, V_C = 20~\text{V}~\text{and}~V_R = 15~\text{V}.\) The supply voltage will be:
1. \(25~\text{V}\)
2. \(75~\text{V}\)
3. \(35~\text{V}\)
4. zero
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