Understanding Parallel Circuits

Key Objectives

• Describe what is meant by a parallel circuit.
• Understand the pattern of current flow in a parallel circuit.

Introduction

• Electric current: Flow of electrical charge around a circuit, moves from the negative to the positive end.
• Conventional current direction: Opposite to the actual flow direction.
• Measurement: Current is measured using an ammeter placed in the circuit.

Series Circuits Recap

• A series circuit has no branches, current flows in one path.
• The current is the same all the way around a series circuit.

Parallel Circuits

• Definition: A parallel circuit contains branches where the current splits.
• Current Splitting: Some of the current passes through each branch.

Current Measurement in Parallel Circuits

• The total current leaving the cell splits through the branches.
• Example:
  • Current leaving the cell: 0.3 A.
  • Upper branch current: 0.1 A.
  • Lower branch current: 0.2 A.
  • Current going back to the cell: 0.3 A.
• Key Fact: The current in the branches adds up to the total current leaving the cell.

Practice Questions

1. Question: Work out the current in the lower branch.

   • Given: Current leaving the cell = 0.5 A; Current in upper branch = 0.3 A.
   • Solution: Lower branch current = 0.5 A - 0.3 A = 0.2 A.

2. Question: Determine the current leaving the cell.

   • Given: Upper branch current = 0.4 A; Lower branch current = 0.3 A.
   • Solution: Current leaving the cell = 0.4 A + 0.3 A = 0.7 A.

Conclusion

• Understand how to describe a parallel circuit and the pattern of current flow.
• Next steps: Exploration of what determines the amount of current in different branches of a parallel circuit.

Additional Resources

• Vision Workbook for more practice questions on current and parallel circuits.

Visual Resources

• Link to workbook and further materials for revision.