In an electrical circuit \(R,\) \(L,\) \(C\) and an \(\mathrm{AB}\) voltage source are all connected in series. When \(L\) is removed from the circuit, the phase difference between the voltage and the current in the circuit is \(\tan^{-1}\sqrt{3}\). If instead, \(C\) is removed from the circuit, the phase difference is again \(\tan^{-1}\sqrt{3}\). The power factor of the circuit is:
1. \(1 / 2 \)
2. \(1 / \sqrt{2} \)
3. \(1 \)
4. \(\sqrt{3} / 2\)
An AC voltage is applied to a resistance R and an inductor L in series. If R and the inductive reactance are both equal to 3 , the phase difference between the applied voltage and the current in the circuit is:
1.
2.
3. zero
4.
In the given circuit, the reading of voltmeter V1 and V2 are 300 V each. The reading of the voltmeter V3 and ammeter A are respectively:
1. 150 V, 2.2 A
2. 220 V, 2.2 A
3. 220 V, 2.0 A
4. 100 V, 2.0 A
A \(220\) V input is supplied to a transformer. The output circuit draws a current of \(2.0\) A at \(440\) V. If the efficiency of the transformer is \(80\)%, the current drawn by the primary windings of the transformer is:
1. \(3.6\) A
2. \(2.8\) A
3. \(2.5\) A
4. \(5.0\) A
The power dissipated in an L-C-R series circuit connected to an AC source of emf E is:
In an AC circuit, the emf (e) and the current (I) at any instant are given respectively by
e = E0sint
I = I0sin
The average power in the circuit over one cycle of AC is:
1.
2.
3.
4.
What is the value of inductance L for which the current is maximum in a series LCR circuit with C = 10 μF and ω=1000 s-1?
1. 100 mH
2. 1 mH
3. cannot be calculated unless R is known
4. 10 mH
A transformer is used to light a \(100\) W and \(110\) V lamp from a \(220\) V main. If the main current is \(0.5\) A, the efficiency of the transformer is approximately:
1. \(30\%\)
2. \(50\%\)
3. \(90\%\)
4. \(10\%\)
The core of a transformer is laminated so that:
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. | the ratio of voltage in primary and secondary may be increased |