AQA GCSE Parallel Circuits

Parallel Circuits

A parallel circuit contains electrical components that are in a branched circuit.

Rules for Parallel Circuit diagram

Rule 1: The potential difference is the same across each component in a parallel circuit

In the circuit above, the potential difference is the same across all components

Rule 2: In a parallel circuit, total current through the whole circuit is the sum of the
currents through the separate components.

This means that at a junction, the current splits. Think of this just like the water flow splits in a pipe at a junction.

Rule 3: The total resistance in a parallel circuit is less than the value of resistance for the lowest single resistor.

In the circuit diagram above the total resistance will be lower than the resistor with the least value. In this case, total resistance is < 2 ohms.

You do not need to know how to calculate the exact value on AQA.

You do need to know that as more resistors are added in parallel, total resistance decreases because this is adding more branches to the circuit, so there are more routes for the current to flow.

Practice Questions

1.In the circuit below calculate the value for the potential difference across both the cell and one of the bulbs.

2. Calculate the missing value for current for the ammeters in the circuit below. Assume that all bulbs are identical.

3. A parallel circuit contains 3 resistors, wired in parallel 10 ohm, 5 ohm and 4 ohm resistor. State the value for the total resistance of the circuit.