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Browse complete papersA balanced three-phase load draws a line current of 25 A at a line voltage of 400 V. If the power factor is 0. 9 lagging, what is the total real power consumed by the load?
25 kW
Correct answer
The working principle of a moving coil galvanometer is based on the effect of a magnetic field on a:
Insulator
Stationary charge
Moving magnet
Current-carrying conductor
Correct answer
Insulator
The time period of oscillation of a galvanometer coil is 2 s. If the torsional constant of the suspension fiber is increased by a factor of 4 and the moment of inertia of the coil is halved, what is the new time period of oscillation?
Correct answer
How is the current coil of an analog wattmeter connected in a circuit?
In series with the voltage coil.
In parallel with the load
In series with the load
Only at the power source
Correct answer
In series with the voltage coil.
A lagging power factor is typically caused by which type of load?
Purely reactive loads
Inductive Loads
Capacitive loads
Resistive loads
Correct answer
Purely reactive loads
What is the most common method used to improve a lagging power factor?
Installing inductors in parallel with the load.
Installing capacitors in parallel with the load
Installing resistors in series with the load
Installing transformers to increase voltage
Correct answer
Installing inductors in parallel with the load.
A load with an apparent power of 25 kVA and a power factor of 0. 8 lagging needs to be improved to a power factor of 0. 95 lagging. What is the new apparent power (in kVA) after correction?
25 kVA
20 kVA
Correct answer
25 kVA
8 A load with an impedance of (5+j12)\(\Omega\) is connected to a 200 V source. A parallel capacitor is added to bring the power factor to unity. What is the value of the capacitance in µF if the frequency is 50 Hz?
42.8 μF
226 µF
56.2 µF
74.6 µF
Correct answer
42.8 μF
Which of the following statements about the reverse saturation current in a p-n junction diode is most accurate?
It is equal to the forward current when the diode is in forward bias.
It increases significantly with an increase in reverse bias voltage.
It is highly dependent on the temperature of the diode.
It is primarily due to the diffusion of majority carriers across the junction.
Correct answer
It is equal to the forward current when the diode is in forward bias.
In a mercury arc rectifier, what is the primary function of the anodes?
To heat the mercury vapor to start the rectification process
To attract the positive mercury ions to maintain the arc
To collect the electrons emitted from the cathode
To serve as the main source of electron emission
Correct answer
To heat the mercury vapor to start the rectification process