Series and Parallel Circuits

This lesson covers the rules for series and parallel circuits, including how current, potential difference and resistance behave in each arrangement, as required by AQA GCSE Combined Science Trilogy (8464, section 6.2.1).

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Series Circuits

A series circuit has only one loop — all components are connected end-to-end, and 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

Rules for Series Circuits

1. Current

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

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

This is because there is only one path for the charge to flow through — every electron must pass through every component.

2. Potential Difference

The potential differences across the components add up to give the total p.d. of the supply.

$V_{\text{total}} = V_1 + V_2 + V_3$Vtotal​=V1​+V2​+V3​

The voltage is shared between the components. A component with a higher resistance gets a larger share of the voltage.

3. Resistance

The total resistance is the sum of the individual resistances.