GCSE Physics (AQA)

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Electrical Power in Terms of Resistance

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Electricity Energy transfers

Electrical Power in Terms of Resistance

2:07 Electrical Energy and Power
Spec 4.2.4.1
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  • Combine equations for power and resistance to form an equation for power in terms of resistance.
  • Power (P) equals current (I) times voltage (V), and voltage (V) equals current (I) times resistance (R).
  • Substitute voltage into the power equation: P = I * IR or P = I��R.
  • Power equals current squared multiplied by resistance.
  • Current is measured in amps, resistance in ohms, and power in watts.
  • Useful equation when potential difference is unknown.
  • Example: Calculate resistance of a lamp in a circuit with a 6-watt lamp and 2 amps current.
  • Step 1: Write down key information and check units (Power = 6 watts, Current = 2 amps).
  • Step 2: Rearrange power equation to make resistance the subject: Resistance = Power / Current��.
  • Step 3: Substitute values into rearranged equation: Resistance = 6 watts / (2 amps)�� = 1.5 ohms.

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