Series & Parallel Circuits
Year 8 ⚡ Electricity & Magnetism Compare current and voltage in series and parallel circuits.
🔗 Series Circuits
In a series circuit, all components are connected in one single loop. Current has only one path to flow through.
🔗 Series Circuit Rules
$$I_{\text{total}} = I_1 = I_2 = I_3 \quad \text{(same current everywhere)}$$
$$V_{\text{total}} = V_1 + V_2 + V_3 \quad \text{(voltages add up)}$$
$$R_{\text{total}} = R_1 + R_2 + R_3 \quad \text{(resistances add up)}$$💡 Old Christmas lights: Wired in series — if ONE bulb blows, the whole string goes out! That's why modern lights use parallel wiring.
⚡ Parallel Circuits
In a parallel circuit, components are on separate branches. Current can take multiple paths.
⚡ Parallel Circuit Rules
$$V_{\text{total}} = V_1 = V_2 = V_3 \quad \text{(same voltage on each branch)}$$
$$I_{\text{total}} = I_1 + I_2 + I_3 \quad \text{(currents add up)}$$
$$\frac{1}{R_{\text{total}}} = \frac{1}{R_1} + \frac{1}{R_2} + \frac{1}{R_3} \quad \text{(total resistance decreases!)}$$🏠 Home wiring: All appliances are wired in parallel — each gets the full 230 V mains voltage, and switching off one doesn't affect the others!
🔌 Comparing Circuit Types
Series and parallel circuits behave very differently.
| 📊 Property | 🔗 Series | ⚡ Parallel |
|---|---|---|
| Current path | One loop | Multiple branches |
| Current | Same everywhere | Splits at junctions |
| Voltage | Splits across components | Same across each branch |
| Total resistance | Increases (sum) | Decreases (less than smallest R) |
| One component fails | All stop working | Others keep working |
| Used in... | Simple switches, some sensors | Home wiring, car systems |
Adding more resistors in parallel always decreases total resistance — giving more paths for current to flow!
Ready to test yourself? Click the Quiz tab above to answer questions on this topic!
🔌 Series & Parallel Resistance Calculator