Electrical Charge and Current

Aug 24, 2025

Overview

The lecture explains how to calculate electrical charge flow in a circuit using the relationship between current, time, and charge.

Electric Current and Charge Flow

  • Electric current is the rate at which electrical charge flows through a circuit.
  • Electrical charge is measured in coulombs (symbol: C).
  • A current of 1 ampere (A) means 1 coulomb of charge passes a point in the circuit per second.

Charge Flow Equation

  • The equation: Charge flow (Q, in coulombs) = Current (I, in amperes) × Time (t, in seconds).
  • This equation is not provided in exams and must be memorized.

Example Calculations

  • To find charge: Multiply current by time (e.g., Q = 0.3 A × 20 s = 6 C).
  • To find current: Rearrange to Current = Charge flow ÷ Time (e.g., I = 360 C ÷ 400 s = 0.9 A).

Key Terms & Definitions

  • Electric current — the rate of flow of electrical charge.
  • Coulomb (C) — the unit of electrical charge.
  • Ampere (A) — the unit of electric current; 1 A = 1 C per second.

Action Items / Next Steps

  • Memorize the charge flow equation: Q = I × t.
  • Practice more charge flow calculation questions from the vision workbook.