Question

1. In an A.C circuit with an inductor and a resistor, current leads source voltage.
2. In an R.L.C circuit, current may lead source voltage.
3. In an A.C circuit with a capacitor and a resistor, current leads source voltage.
4. Up on increasing the frequency of a source, power factor decreases.

• A. All statements are true.
• B. 2 and 3 are true.
• C. 2, 3 and 4 are true.
• D. 1 and 4 are true.

Answer 1

The correct option is B 2 and 3 are true.

1) In a phasor diagram with an inductor and a resistor, the resultant is in the 4th quadrant. So the phase is negative. So current lags.
2) In a phasor diagram with a capacitor, inductor and a resistor, the resultant can be in the first or the fourth quadrent depending on the value of capacitance and inductance. So current may lead or may lag.
3) In a phasor diagram with a capacitor and a resistor, the resultant is in the 1st quadrant. So the phase is positive. So current leads.
4) As frequency is increased, impedance of the combination of the inductor and the capacitor may increase or decrease. So, the power factor may increase or decrease.