Series and parallel circuit analysis

Series and parallel circuit analysis

Series and parallel circuits distribute current, potential difference and resistance in different ways. In series, there is one path: current is the same through each component, potential differences add to the supply value, and resistances add. In parallel, branches share the supply potential difference, currents split and recombine, and equivalent resistance is lower than the smallest branch resistance because there are more paths for charge. Analyse the circuit one quantity at a time and label which network or branch an equation applies to. A household circuit is wired in parallel so appliances can operate independently at the supply potential difference.

Work it through

A 6 Ω and 3 Ω resistor in parallel have 1/Req = 1/6 + 1/3 = 3/6, so Req = 2 Ω. The result is less than 3 Ω, as it must be for parallel branches. In series the same two resistors would give 9 Ω. This comparison checks both the calculation and the circuit classification.

Mastery target

Recognise series and parallel structure, calculate simple equivalent resistance and use conservation of charge and energy to explain current and voltage patterns.