Parallel Circuits

This lesson covers the rules governing parallel 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 separate branches.

---

What Is a Parallel Circuit?

In a parallel circuit, components are connected on separate branches so that the current has more than one path to follow.

flowchart TD
    A["Battery"] --> B["Junction"]
    B --> C["Lamp 1"]
    B --> D["Lamp 2"]
    C --> E["Junction"]
    D --> E
    E --> A

Each branch provides an independent path. If one branch is disconnected, current can still flow through the other branches.

---

Rule 1: Voltage Is the Same Across Each Branch

In a parallel circuit, the potential difference across each branch is the same as the potential difference supplied by the battery.

$V_{\text{battery}} = V_1 = V_2 = V_3$Vbattery​=V1​=V2​=V3​

Why?

Each branch is connected directly to the battery terminals. Every branch therefore receives the full voltage of the supply.

Worked Example 1

A 6 V battery is connected to two lamps in parallel. What is the voltage across each lamp?

$V_1 = V_2 = 6 \text{ V}$V1​=V2​=6 V