Series Circuits

This lesson covers the rules governing series circuits, as required by the Edexcel GCSE Combined Science specification (1SC0). You will learn how current, voltage and resistance behave when components are connected in a single loop.

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What Is a Series Circuit?

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

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

If any component breaks or is disconnected, the entire circuit stops working because the single loop is broken.

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Rule 1: Current Is the Same Everywhere

In a series circuit, the current is the same at every point in the circuit.

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

Why?

There is only one path, so every coulomb of charge that leaves the battery must pass through every component. Charge is conserved — it is not used up or created anywhere in the circuit.

Worked Example 1