GCSE Physics · Edexcel 1PH0 · Topic 10B
Series and parallel circuits
Key points
- Series: one loop. Current is the same at every point. The supply pd is shared between components. Total resistance
- Parallel: separate branches. The pd across each branch equals the supply pd. The total current is the sum of the branch currents.
- Adding a resistor in parallel decreases the total resistance, because there are more paths for the current.
- The total resistance of resistors in parallel is less than the smallest individual resistor.
- Household lights are in parallel so each can be switched on and off independently and one failing does not stop the others.
- A potential divider uses two resistors in series; a larger resistor gets a larger share of the pd.
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Components can be joined one after another in a single loop (series) or side by side on separate branches (parallel). The two arrangements follow different rules, and knowing them lets you work out any current or pd in a simple circuit.
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