Revise Potential difference and power for Cambridge 9702 (9.2)

Potential difference, often shortened to p.d. or simply voltage, tells us how much energy is transferred when a unit of charge moves between two points in a circuit. Essentially, it quantifies the "energy push" that charges receive (e.g., from a battery) or the "energy drop" as they pass through a component (e.g., a resistor).

$V = \frac{\Delta W}{\Delta Q}$

Electrical power is all about speed – specifically, the rate at which electrical energy is transferred, supplied, or dissipated within a circuit. It measures how quickly electrical energy transforms into other forms, such as heat, light, or mechanical energy in devices like motors.

$P = \frac{\Delta E}{\Delta t}$

We can combine the definitions of potential difference, current, and Ohm's Law to derive several crucial formulas for electrical power. These equations are fundamental for analysing circuits and calculating power dissipation or supply based on the known quantities.

$P = VI$

$P = I^2R$

$P = \frac{V^2}{R}$

While power describes the rate of energy transfer, sometimes you need to know the total amount of energy transferred over a specific period. This is simply the power multiplied by the duration for which the component or circuit was operating.

$E = VIt$