Fundamentals of AC Circuits

All over the world, sinusoidal voltages and currents are selected for generation of electrical power because:

• produce low iron and copper losses

• offer less interference to nearby communication lines

• produce less disturbance in the network

• All the above

RMS value for an AC quantity can be applied to

• Symmetrical waveforms

• Unsymmetrical waveforms

• Both symmetrical & unsymmetrical waveforms

• None of the above

The steady or DC current which when flowing through a circuit for a given time period produces the same heat as produced by the AC current flowing through the same circuit for the same time period is called as _________ of an AC quantity.

• RMS value

• Maximum value

• Instantaneous value

• Average value

Definitions of power factor of a series R-L-C circuit are correct except

• Ratio of net reactance and impedance

• Ratio of kW and kVA

• Ratio of R and Z

• Ratio of W and VA

If two sinusoids of the same frequency but of different amplitudes and phase angles are subtracted, the resultant is

• A sinusoid of double the frequency

• A sinusoid of the same frequency

• A sinusoid of half the original frequency

• None of the above

All the rules and laws of D.C. circuit also apply to A.C. circuit containing

• Capacitance only

• Inductance only

• Resistance only

• All above

In an A.C. circuit power is dissipated in

• Resistance only

• Inductance only

• Capacitance only

• In all the three passive elements

In a pure inductive circuit if the supply frequency is reduced to 1/2, the current will

• Be reduced by half

• Be doubled

• Be four times as high

• Be reduced to one fourth

The time constant of a series R-C circuit is given by

• R/C

• RC²

• R²C

• RC

A heater is rated as 230 V, 10 kW, 50 Hz AC. The value 230 V refers to

• Average voltage

• r.m.s. voltage

• Peak voltage

• None of the above