Overview
This lecture covers how to calculate the total energy transferred by components in an electrical circuit using charge, current, time, and potential difference.
Calculating Charge in a Circuit
- The total charge (Q) is found by multiplying current (I, in amperes) by time (t, in seconds): Q = I × t.
- Example: For a current of 0.3 A over 10 seconds, Q = 0.3 × 10 = 3 coulombs (C).
Calculating Energy Transferred
- Energy transferred (E, in joules) is calculated as charge (Q) multiplied by potential difference (V, in volts): E = Q × V.
- This equation is not given in exams and must be memorized.
- Example: If 4 C of charge flows through a circuit with 15 V, energy transferred is 4 × 15 = 60 J.
Series Circuits and Potential Difference
- In series circuits, the total potential difference is shared among components.
- To find the potential difference across one resistor, subtract the potential difference across the other from the total.
- Example: If total V is 30 V, resistor B has 25 V, then resistor A has 5 V.
Example Problem: Energy Transferred in a Resistor
- Use E = Q × V for specific components.
- Example: 3 C of charge flows through resistor A with 5 V across it, so energy transferred is 3 × 5 = 15 J.
Key Terms & Definitions
- Charge (Q) — The quantity of electricity, measured in coulombs (C).
- Current (I) — The flow of electric charge, measured in amperes (A).
- Time (t) — Duration, measured in seconds (s).
- Potential Difference (V) — The energy per charge between two points, measured in volts (V).
- Energy Transferred (E) — The work done or energy moved, measured in joules (J).
- Series Circuit — A circuit with components arranged in a single loop, sharing total voltage.
Action Items / Next Steps
- Memorize the equation E = Q × V.
- Practice more calculations from the provided revision workbook or similar resources.
- Review concepts of current, charge, potential difference, and energy calculations for circuit components.