Resistors in Series & Parallel (OCR GCSE Physics A, Combined (Gateway Science Suite)): Revision Notes

When resistors are connected in series, the total resistance is the sum of the individual resistances:

This is because the current must pass through each resistor, adding to the overall resistance of the circuit.

• Resistance (R) is measured in ohms (Ω)

When resistors are connected in parallel, the combined resistance is always less than the smallest individual resistor. The total or combined resistance $R_{\text{total}}$ for resistors in parallel is found using the formula:

This is because, in a parallel circuit, the current has multiple paths to take, reducing the overall resistance. As more resistors are added in parallel, the total resistance decreases.

• Like in series circuits, resistance is measured in ohms (Ω).