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Practice each question, then open the answer or worked solution.
If the rms current in a 50 Hz ac circuit is 5 A, the value of the current 1/300 seconds after its value becomes zero is
(a) 5 √2 A
(b) 5 √3/2 A
(c) 5/6 A
(d) 5/ √2 A
(b) 5 √3/2 A
An alternating current generator has an internal resistance Rg and an internal reactance Xg. It is used to supply power to a passive load consisting of a resistance Rg and a reactance XL. For maximum power to be delivered from the generator to the load, the value of XL is equal to
(a) zero.
(b) Xg.
(c) – Xg.
(d) Rg .
(c) – Xg.
When a voltage measuring device is connected to AC mains, the meter shows the steady input voltage of 220V. This means
(a) input voltage cannot be AC voltage, but a DC voltage.
(b) maximum input voltage is 220V.
(c) the meter reads not v but <v2> and is calibrated to read √<v2> .
(d) the pointer of the meter is stuck by some mechanical defect.
(c) the meter reads not v but <v2> and is calibrated to read √<v2>
To reduce the resonant frequency in an LCR series circuit with a generator
(a) the generator frequency should be reduced.
(b) another capacitor should be added in parallel to the first.
(c) the iron core of the inductor should be removed.
(d) dielectric in the capacitor should be removed.
(b) another capacitor should be added in parallel to the first
Which of the following combinations should be selected for better tuning of an LCR circuit used for communication?
(c) R = 15 Ω, L = 3.5 H, C = 30µF.
An inductor of reactance 1 Ω and a resistor of 2 Ω are connected in series to the terminals of a 6 V (rms) a.c. source. The power dissipated in the circuit is
(a) 8 W.
(b) 12 W.
(c) 14.4 W.
(d) 18 W.
(c) 14.4 W.
The output of a step-down transformer is measured to be 24 V when connected to a 12 watt light bulb. The value of the peak current is
(a) 1/ √2 A.
(b) √2 A.
(c) 2 A.
(d) 2 √2 A
(a) 1/ √2 A.
Multiple Choice Questions IIAs the frequency of an ac circuit increases, the current first increases and then decreases. What combination of circuit elements is most likely to comprise the circuit?
(a) Inductor and capacitor.
(b) Resistor and inductor.
(c) Resistor and capacitor.
(d) Resistor, inductor and capacitor.
(a) Inductor and capacitor.
(d) Resistor, inductor and capacitor.
In an alternating current circuit consisting of elements in series, the current increases on increasing the frequency of supply. Which of the following elements are likely to constitute the circuit?
(c) Resistor and a capacitor.
(d) Only a capacitor.
Electrical energy is transmitted over large distances at high alternating voltages. Which of the following statements is (are) correct?
(a) For a given power level, there is a lower current.
(b) Lower current implies less power loss.
(d) It is easy to reduce the voltage at the receiving end using step-down transformers.