Physics Lecture: Solving Assignment 12.3

Introduction

• Lecturer: Atif Ahmed, Physics Teacher
• Topic: Solving Assignment 12.3 on calculating the current in a branch of a given circuit

Steps to Solve the Assignment

1. Understand the Circuit: Basic Overview

   • Given circuit has a single battery and the current (I) is dividing into two parts.
   • Goal: Calculate the current in each branch.
   • Method: Use voltage application and given formulas to solve the circuit.

2. Preparation and Drawing the Circuit Diagram

   • Draw the circuit diagram based on the provided details.
   • Label key points in the circuit as A, B, C, D, E, F, etc.

3. Selecting the Loops

   • Select loops for analysis, which must include at least one resistor.
   • Label the loops sequentially, e.g., Loop 1 (A-B-C-D), Loop 2 (A-F-E-B-C).
   • Name resistances as R1, R2, R3, R4 and assign values to each.

4. Assume the Direction of Current

   • Current direction can be clockwise (CW) or counterclockwise (CCW).
   • For consistency, apply the same current direction to all loops.
   • Label currents I1 and I2 for Loop 1 and Loop 2 respectively.

5. Apply Kirchhoff's Voltage Law (KVL) to Each Loop

   • Write KVL equations for each loop considering EMF (Electromotive Force) and resistances.
   • Account for potential differences as current flows through each resistor (V = IR).
   • Important: Negative sign for resistors always (energy consumption).

6. Solving the KVL Equations

   • For Loop 1: Write the equation considering net voltage = 0.
   • For Loop 2: Repeat the process ensuring all terms are included correctly.
   • Simplify the equations by substituting the known resistance values.

7. Equation Simplification and Manipulation

   • Combine and simplify terms to isolate I1 and I2.
   • Example Equation Summarization:
     • Loop 1: 25I1 - 15I2 = 3
     • Loop 2: 3I1 - 17I2 = 0
   • Use algebraic methods to solve these simultaneous equations.

8. Substitute to Find Currents

   • Use one solved value to substitute and find the other.
   • Example: I1 = 17/3 * I2;
   • Calculate numeric values for I1 and I2 using a calculator:
     • I2 ≈ 0.02364A
     • I1 ≈ 0.1342A

9. Cross-Verification

   • Ensure no calculation errors by substituting back into the equations.
   • Calculate current through other branches if needed based on these values.

10. Conclusion and Review

• Verify the overall solution aligns with the problem statement.
• Ensure the method and each step logically follow and attend to each circuit element.

Summary

• Teacher emphasized following the correct methodology for solving circuit problems using KVL.
• Importance of consistency in current direction and correct sign application for each term.
• Steps ensure correct, logical progress leading to accurate results.
• Encouraged to review and verify each step for possible errors.
• Practical application strengthens understanding of fundamental circuit analysis techniques.

Additional Notes

• Like and subscribe to the channel if the video helped you.
• Share with peers who might benefit from these methods.