Math Problem Statement

Answer

A parallel RLC circuit has a resistor of 30Ω, an inductor of 50 mH, and a capacitor of 50 μF connected across 240 V, 50 Hz supply. Calculate various parameters such as resistive branch current, inductive reactance, phase angles, etc.

Solution

The given problem concerns a parallel RLC AC circuit that consists of a resistor (30 Ω), an inductor (50 mH), and a capacitor (50 μF), connected across a 240 V, 50 Hz supply. Let's break it down step by step:

Circuit Parameters:

  • Resistor (R) = 30 Ω
  • Inductor (L) = 50 mH = 50×103H50 \times 10^{-3} \, \text{H}
  • Capacitor (C) = 50 μF = 50×106F50 \times 10^{-6} \, \text{F}
  • Supply Voltage (V) = 240 V
  • Frequency (f) = 50 Hz

Required Calculations:

(a) Resistive Branch Current: Using Ohm's Law for the resistive branch: IR=VR=24030=8AI_R = \frac{V}{R} = \frac{240}{30} = 8 \, \text{A}

(b) Inductive Reactance (X_L): XL=2πfL=2π(50)(50×103)=15.71ΩX_L = 2\pi f L = 2\pi (50)(50 \times 10^{-3}) = 15.71 \, \Omega

(c) Inductive Branch Current: For the inductive branch: IL=VXL=24015.7115.28AI_L = \frac{V}{X_L} = \frac{240}{15.71} \approx 15.28 \, \text{A}

(d) Impedance of Inductive Branch: The impedance in the inductive branch is purely reactive (since there's no resistance), so: ZL=XL=15.71ΩZ_L = X_L = 15.71 \, \Omega

(e) Phase Angle of Inductive Branch: In a purely inductive circuit, the current lags the voltage by 9090^\circ: θL=90\theta_L = -90^\circ

(f) Capacitive Reactance (X_C): XC=12πfC=12π(50)(50×106)63.66ΩX_C = \frac{1}{2\pi f C} = \frac{1}{2\pi (50)(50 \times 10^{-6})} \approx 63.66 \, \Omega

(g) Capacitive Branch Current: For the capacitive branch: IC=VXC=24063.663.77AI_C = \frac{V}{X_C} = \frac{240}{63.66} \approx 3.77 \, \text{A}

(h) Capacitive Branch Impedance: Again, the impedance in the capacitive branch is purely reactive: ZC=XC=63.66ΩZ_C = X_C = 63.66 \, \Omega

Next Steps:

Now that we have the individual branch currents and reactances, we can proceed to the following:

(i) Circuit Current: The total current is found by combining the currents of all branches (resistive, inductive, and capacitive). Since these are out of phase, they must be added vectorially.

(j) Circuit Impedance: The impedance of the entire circuit can be found by using the total current and voltage.

(k) Phase Angle of the Circuit: This can be calculated based on the total impedance.

(l) Phasor Diagram: Finally, the phasor diagram can illustrate the phase relationships between the currents and voltages in each branch.

Would you like me to continue with these steps, or do you have any specific questions about the steps so far?

5 Related Questions:

  1. How do we calculate the total current in a parallel RLC circuit?
  2. What is the significance of the phase angle in AC circuits?
  3. How do you construct a phasor diagram for an RLC circuit?
  4. Why does the current lead the voltage in a capacitive circuit but lag in an inductive circuit?
  5. How does changing the frequency affect the reactances of the inductor and capacitor?

Tip:

In a parallel RLC circuit, the total current is the phasor sum of the branch currents, as they are out of phase with each other. Always remember to account for phase differences when calculating total current.

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Math Problem Analysis

Mathematical Concepts

Ohm's Law
Inductive Reactance
Capacitive Reactance
Impedance in AC Circuits
Phase Angle in RLC Circuits

Formulas

Resistive Branch Current: I_R = V/R
Inductive Reactance: X_L = 2πfL
Capacitive Reactance: X_C = 1/(2πfC)
Inductive Branch Current: I_L = V/X_L
Capacitive Branch Current: I_C = V/X_C

Theorems

Ohm's Law
Reactance in AC Circuits
Phasor Addition of Currents

Suitable Grade Level

College-Level Electrical Engineering