Overview
This lecture explains how to calculate the power of electrical components using key formulas involving potential difference, current, and resistance in electric circuits.
Power and Energy Transfer
- Power is the rate at which energy is transferred in a circuit.
- The unit of power is the watt (W), where 1 watt equals 1 joule (J) per second.
- Energy is transferred in a circuit when charge moves through components like resistors.
Calculating Power Using Potential Difference and Current
- The power (P) of a component can be calculated with: P = V × I.
- V is potential difference (voltage) in volts (V), I is current in amperes (A).
- Example: With 50 V across a resistor and 0.2 A current, power is 50 × 0.2 = 10 W.
Series Circuits and Potential Difference
- In series circuits, total potential difference is shared between components.
- To find the potential difference across one resistor, subtract the voltage across the other from the total.
- Example: If total voltage is 20 V, and one resistor has 15 V, the other has 5 V.
- Power can then be found using P = V × I.
Calculating Power Using Current and Resistance
- If current (I) and resistance (R) are known, use: P = I² × R.
- I is current in amperes (A), R is resistance in ohms (Ω).
- Example: With 0.4 A current and 50 Ω resistance, power is (0.4)² × 50 = 8 W.
Key Terms & Definitions
- Power (P) — Rate of energy transfer, measured in watts (W).
- Potential Difference (V) — Voltage across a component, measured in volts (V).
- Current (I) — Flow of electric charge, measured in amperes (A).
- Resistance (R) — Opposition to current, measured in ohms (Ω).
- Joule (J) — Unit of energy.
Action Items / Next Steps
- Memorize the formulas: P = V × I and P = I² × R (not provided in exams).
- Practice more power calculation questions in the revision workbook if available.