Series and Parallel Circuits

This lesson covers the rules for series and parallel circuits — as required by the Edexcel GCSE Physics specification (1PH0). You need to understand how current, voltage and resistance behave in each type of circuit, and be able to carry out calculations using these rules.

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Series Circuits

In a series circuit, all components are connected one after another in a single loop. There is only one path for the current to take.

graph LR
    A["Battery"] --> B["Lamp 1"]
    B --> C["Lamp 2"]
    C --> D["Lamp 3"]
    D --> A

    style A fill:#2c3e50,color:#fff
    style B fill:#e67e22,color:#fff
    style C fill:#e67e22,color:#fff
    style D fill:#e67e22,color:#fff

Rules for Series Circuits

1. Current Is the Same Everywhere

The current is the same at every point in a series circuit. There is only one path, so all the charge must flow through every component.

$I_{total} = I_1 = I_2 = I_3$Itotal​=I1​=I2​=I3​

If the ammeter reads 0.5 A anywhere in the circuit, it reads 0.5 A everywhere in that circuit.

2. Voltage Is Shared Between Components