Electrical Power and Energy

This lesson covers electrical power and energy transfer calculations — as required by the Edexcel GCSE Physics specification (1PH0). You need to be confident using several key equations, converting between units, and calculating electricity costs. These topics appear frequently in exam calculations.

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Electrical Power

Power is the rate of energy transfer — it tells you how much energy a device transfers per second.

Key Equations for Power

There are three equations you need to know:

Equation 1:

$P = IV$P=IV

Where:

• P = power (watts, W)
• I = current (amperes, A)
• V = potential difference (volts, V)

Equation 2:

$P = I^2 R$P=I2R

Where:

• P = power (watts, W)
• I = current (amperes, A)
• R = resistance (ohms, Ω)

Equation 3:

$P = \frac{V^2}{R}$P=RV2​

Where:

• P = power (watts, W)
• V = potential difference (volts, V)
• R = resistance (ohms, Ω)

How the Equations Are Related

All three can be derived from P = IV and V = IR: