All Exams Test series for 1 year @ ₹349 only
Question

How is the phase angle between voltage V and total current I in a S parallel RLC circuit determined?

This question was previously asked in
RRB JE 2025 CBT 2 Mechanical and Allied Engg Question Paper English (2-Jul-2026) (Shift-1)
The correct answer is

From the angle between V and the vector sum of I R , I L , and I C

To determine the phase angle between the voltage \( V \) and the total current \( I \) in a series or parallel RLC (Resistor, Inductor, Capacitor) circuit, it is important to understand the concept of phasors and impedance in AC circuits.

In a parallel RLC circuit, the total current \( I \) is the phasor sum of the currents through the resistor (\( I_R \)), inductor (\( I_L \)), and capacitor (\( I_C \)). These currents are typically out of phase with each other due to the reactance of the inductor and capacitor.

The phase angle \(\phi\) between the voltage \( V \) and the total current \( I \) is derived from the relationship between the total impedance \( Z \) of the circuit and the reactive components. The total impedance \( Z \) in a parallel RLC circuit can be calculated using the formula:

Z = \frac{1}{\sqrt{(\frac{1}{R})^2 + (\frac{1}{X_L} - \frac{1}{X_C})^2}}

Where:

  • R is the resistance.
  • X_L = \omega L is the inductive reactance, where \omega is the angular frequency and L is the inductance.
  • X_C = \frac{1}{\omega C} is the capacitive reactance, where C is the capacitance.

The phase angle is given by the angle of the total impedance vector relative to the horizontal axis (real component = resistive part). It can be expressed as:

\phi = \tan^{-1}\left(\frac{I_L - I_C}{I_R}\right)

Based on the given options, the correct way to determine this phase angle is through the angle between the voltage \( V \) and the vector sum of the currents \( I_R \), \( I_L \), and \( I_C \). This is option:

From the angle between V and the vector sum of I R, I L, and I C

Other options do not correctly explain how to determine the phase angle:

  • Comparing voltage drops across each element does not give direct phase angle for parallel RLC circuits.
  • Finding the angle between \( V \) and \( I_R \) alone ignores the effects of reactance from \( I_L \) and \( I_C \).
  • Subtracting \( I_L \) from \( I_C \) gives the net reactive current but not the phase angle directly from total impedance.
Was this answer helpful?

Similar Questions

  1. In a single-phase parallel RL circuit connected to a single phase AC supply, which of the following is correct?

  2. In a parallel RC circuit connected to a single-phase AC supply, the correct relationship between the supply voltage and the total circuit current is _________.

  3. An oscilloscope displays a measured rise time of 10 ns when observing a fast pulse. If the oscilloscope itself has a specified rise time of 6 ns, then what is the approximate actual rise time of the signal being measured?


Important Questions from Phasor Diagrams

  1. In phasor representation of an alternating quantity, the sinusoidally varying alternating quantity can be represented graphically by:

  2. In a single-phase parallel RL circuit connected to a single phase AC supply, which of the following is correct?

  3. In a parallel RC circuit connected to a single-phase AC supply, the correct relationship between the supply voltage and the total circuit current is _________.

  4. An oscilloscope displays a measured rise time of 10 ns when observing a fast pulse. If the oscilloscope itself has a specified rise time of 6 ns, then what is the approximate actual rise time of the signal being measured?

Need Expert Advice?
Test Series
RRB JE img
Railways
RRB JE (CBT 1 + CBT 2) 2026 Mock Test Series
1509 Tests 19 Tests Free
733 Attempts
4.4(121)
English, Hindi

Start Your Preparation with Prepp Mobile App

Download the app from Google Play & App Store
Download the app from Google Play & App Store
Prepp Mobile App