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Q. No.Subtopic: RMS & Average Values |
76%
Level 2: 60%+
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Two coils \(A\) and \(B\) are connected in series across a \(240~\text{V}, ~50~\text{Hz}\) supply. The resistance of \(A\) is \(5~\Omega\) and the inductance of \(B\) is \(0.02~\text{H}\). The power consumed is \(3~\text{kW}\) and the power factor is \(0.75\). The impedance of the circuit is:
1. \(0.144~\Omega\)
2. \(1.44~\Omega\)
3. \(14.4~\Omega\)
4. \(144~\Omega\)
1. \(0.144~\Omega\)
2. \(1.44~\Omega\)
3. \(14.4~\Omega\)
4. \(144~\Omega\)
Subtopic: Power factor |
76%
Level 2: 60%+
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A transformer with \(8:1\) turns ratio has \(50~\text{Hz},\) \(100~\text V\) input. The frequency of the output is:
1. \(40~\text{Hz}\)
2. \(50~\text{Hz}\)
3. \(400~\text{Hz}\)
4. \(500~\text{Hz}\)
1. \(40~\text{Hz}\)
2. \(50~\text{Hz}\)
3. \(400~\text{Hz}\)
4. \(500~\text{Hz}\)
Subtopic: Transformer |
79%
Level 2: 60%+
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An ac voltage source is applied to a LCR series circuit. If the frequency of the source is \(f\), then the expression of impedance will be:
| 1. | \(\sqrt{R^{2}+\left(2 \pi f L-\dfrac{1}{2 \pi f C}\right)^{2}}\) |
| 2. | \(\dfrac{1}{\sqrt{R^{2}+\left(2 \pi f L-\dfrac{1}{2 \pi f C}\right)^{2}}}\) |
| 3. | \( \dfrac{E}{\sqrt{R^{2}+\left(2 \pi f L-\dfrac{1}{2 \pi f C}\right)^{2}}}\) |
| 4. | \(2 \pi f L-\dfrac{1}{2 \pi f C}\) |
Subtopic: Different Types of AC Circuits |
86%
Level 1: 80%+
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An alternating current (AC) flowing in a circuit cannot be measured by a DC-ammeter because:
| 1. | The average value of the current over a complete cycle is zero. |
| 2. | AC does not change its direction after a fixed time interval. |
| 3. | AC can damage the ammeter. |
| 4. | AC is more dangerous than DC. |
Subtopic: RMS & Average Values |
81%
Level 1: 80%+
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A transformer has an efficiency of \(80\text{%}.\) It works at \(40\) kW and \(100\) V. If the secondary voltage is \(240\) V, the current in the secondary coil is nearly:
1. \(40\) A
2. \(133.3\) A
3. \(86.7\) A
4. \(112\) A
1. \(40\) A
2. \(133.3\) A
3. \(86.7\) A
4. \(112\) A
Subtopic: Transformer |
88%
Level 1: 80%+
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A resistor of resistance \(R\) is connected in series with an inductor of inductance \(L\) in an AC circuit. If the phase difference between the applied voltage and the current is \(45^{\circ}, \) the inductive reactance \(X_L\) is:
| 1. | \(R\) | 2. | \(\dfrac{R}{2}\) |
| 3. | \(\dfrac{3R}{2}\) | 4. | \(\dfrac{R}{\sqrt2}\) |
Subtopic: Different Types of AC Circuits |
72%
Level 2: 60%+
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In which of the following circuits, maximum power dissipation is observed?
1. Pure resistive circuit
2. Pure capacitive circuit
3. Pure inductive circuit
4. None of the above
1. Pure resistive circuit
2. Pure capacitive circuit
3. Pure inductive circuit
4. None of the above
Subtopic: Power factor |
88%
Level 1: 80%+
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In an \(LCR\) series circuit connected to an AC voltage source, which option shows the correct voltage across the resistor and the current in the circuit, based on the given values of resistance \((R),\) inductive reactance \((X_L),\) and capacitive reactance \((X_C)?\)
| 1. | \(100~\text{V}; ~5~\text{A}\) | 2. | \(200~\text{V}; ~4~\text{A}\) |
| 3. | \(100~\text{V}; ~2~\text{A}\) | 4. | \(100\sqrt{2}~\text{V}; ~2\sqrt{2}~\text{A}\) |
Subtopic: Different Types of AC Circuits |
78%
Level 2: 60%+
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An ideal transformer has \(100\) turns in the primary coil and carries a \(5\) A current. To achieve a \(1600\) V output with a \(2\) kW power output, the number of turns in the secondary coil must be:
1. \(100\)
2. \(200\)
3. \(300\)
4. \(400\)
1. \(100\)
2. \(200\)
3. \(300\)
4. \(400\)
Subtopic: Transformer |
84%
Level 1: 80%+
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