Series and Parallel Circuits

Every circuit you will encounter at A-Level can be broken down into components connected in series, in parallel, or a combination of both. Mastering the rules for each arrangement is essential for circuit analysis.

---

Series Circuits

In a series circuit, all components are connected end to end in a single loop. There is only one path for the current to flow through.

Three Key Rules for Series Circuits

1. Current is the same through every component.

There is only one path, so the same charge flows through each component every second. If 0.50 A flows through the battery, then 0.50 A flows through every resistor, lamp, or other component in the loop.

2. The total potential difference is shared between the components.

The sum of the potential differences across all components equals the total p.d. of the supply:

V_total = V₁ + V₂ + V₃ + ...

The p.d. across each component is proportional to its resistance (since V = IR and I is the same for all). A larger resistance gets a larger share of the total voltage.

3. The total resistance is the sum of the individual resistances.