Question

The value of power factor, in an AC circuit is zero in
(A) Only inductive circuit
(B) Only resistive circuit
(C) An $L-R$circuit
(D) An $R-C$circuit

Answer 1

Hint: We know that the circuit that is excited using an alternating source is called an AC Circuit. The alternating current (AC) is used for domestic and industrial purposes. In an AC circuit, the value of the magnitude and the direction of current and voltages is not constant, it changes at a regular interval of time. In an alternating-current circuit, voltage periodically reverses itself. When the voltage reverses, so does the direction of the current flow. The electrons in an AC circuit don't really move along with the current flow. Instead, they sort of sit and wiggle back and forth. Based on this concept we have to solve this question.

Complete step-by-step answer:
Power factor (PF) is the ratio of working power, measured in kilowatts (kW), to apparent power, measured in kilovolt amperes (kVA). Apparent power, also known as demand, is the measure of the amount of power used to run machinery and equipment during a certain period.
We know that:
Power factor is a measure of how effectively you are using electricity. Various types of power are at work to provide us with electrical energy.
Power factor, $\cos \phi =\dfrac{R}{Z}$
When circuit contains only resistance, then
$Z=R$
$\therefore \cos \phi =1$
When circuit contains only inductance, then
$R=0$
$\therefore \cos \phi =0$

Hence, the correct answer is Option A and D.

Note We know that the circuit which contains only inductance (L) and not any other quantities like resistance and capacitance in the circuit is called a pure inductive circuit. In this type of circuit, the current lags behind the voltage by an angle of 90 degrees. It is customary to use the angle by which the voltage leads the current. This leads to a positive phase for inductive circuits since current lags the voltage in an inductive circuit. The phase is negative for a capacitive circuit since the current leads the voltage.
It should know that in electricity, containing no, or only very low, inductance. A non-inductive circuit is a circuit in which an alternating current flows in phase, or practically in phase, with the electromotive force.