Table of Contents

- 1 When the voltage and current in the LCR Series AC circuit are in the same phase?
- 2 What is the phase difference between applied AC voltage and the current in an LCR circuit at resonance?
- 3 When current is in phase with voltage?
- 4 When LCR circuit is at resonance then phase angle φ between the current and voltage is?

## When the voltage and current in the LCR Series AC circuit are in the same phase?

Assertion : In series L-C-R, AC circuit, current and voltage are in same phase at resonance. Reason : In series L-C-R, AC circuit, resonant frequency does not depend on the value of resistance. Hence, current at resonance does not depend on resistance.

**When current and voltage are in phase in an AC circuit?**

When capacitors or inductors are involved in an AC circuit, the current and voltage do not peak at the same time. The fraction of a period difference between the peaks expressed in degrees is said to be the phase difference. The phase difference is <= 90 degrees.

**What is phase difference between current and voltage in LCR circuit?**

In an electrical circuit R, L, C and an a.c.voltage source are all connected in series. When L is removed from the circuit, the phase difference between the voltage and the currentin the circuit is π/3.

### What is the phase difference between applied AC voltage and the current in an LCR circuit at resonance?

In an AC circuit containing, L, C and R, the voltage is ahead of current in the inductor by π/2 and the voltage is behind current in the capacitor by π/2. So, the phase difference between the voltage across inductor, VL , and the voltage across capacitor, VC , is π/2 + π/2 = π.

**Why is current maximum at resonance in series LCR circuit?**

So, in a series resonant circuit, voltage across resistor is equal to supply voltage i.e V = Vr. In series RLC circuit current, I = V / Z but at resonance current I = V / R, therefore the current at resonant frequency is maximum as at resonance in impedance of circuit is resistance only and is minimum.

**What is power factor in AC circuits?**

Power factor is defined as the ratio of the average power in an ac circuit to the apparent power, which is the product of the voltage and current magnitudes.

## When current is in phase with voltage?

In this type of circuit, the terms lead, lag, and in phase are used to describe current with reference to voltage. Current is in phase with voltage when there is no phase shift between the sinusoids describing their time varying behavior. This generally occurs when the load drawing the current is resistive.

**What is the phase difference between voltage and current in an AC circuit with pure resistor?**

Hint: A pure resistive circuit consists of an AC source and a resistor. There is no phase difference between voltage and current and the current and voltage is said to be in-phase.

**What is phase difference between EMF and current in series LCR resonant circuit?**

Therefore, the phase difference between applied emf and the line current is zero and the option (D) is correct.

### When LCR circuit is at resonance then phase angle φ between the current and voltage is?

It shows that the phase angle between the current and the voltage is zero. If, ϕ=0 then the power factor is unity.

**Why current in series LCR circuit is maximum at resonance and minimum in parallel LCR circuit?**

Hint: When a series LCR circuit is in resonance, the impedance of the same series LCR circuit is minimum. This happens because the inductance and capacitance are equal in magnitude. As a result of this the current in the series LCR circuit also becomes maximum.

**When a series LCR circuit is in electrical resonance?**

In LCR series circuits, resonance occurs when the value of inductive and capacitive reactances have equal magnitude but have a phase difference of 180°. Thus, they cancel each other. This is known as the resonance frequency of a series LCR circuit.