Unit 6: Electric Circuits
This unit is about how electric circuits function: how current flows, what voltage and resistance mean, and how components behave differently in series and parallel circuits.
01 Current, voltage, resistance
| Quantity | Meaning | Unit |
|---|---|---|
| Current (I) | The flow rate of electric charge | ampere (A) |
| Voltage (V) | The energy given to charge by the source (also called potential difference) | volt (V) |
| Resistance (R) | How much a component opposes the flow of current | ohm (Ω) |
V = I × R (Ohm's Law)
02 Series circuits
In a series circuit, components are connected one after another in a single loop.
- Current is the same at every point
- Voltage is shared between components
- If one component breaks, the whole circuit stops working
03 Parallel circuits
In a parallel circuit, components are connected on separate branches.
- Voltage is the same across each branch
- Current is shared between branches (splits up)
- If one branch breaks, the other branches keep working
Real life: household wiring uses parallel circuits, so one broken lamp does not turn off the whole house.
V Key vocabulary
| Term | Meaning |
|---|---|
| Current | The rate of flow of electric charge, measured in amperes (A). |
| Voltage / potential difference | The energy transferred per unit charge, measured in volts (V). |
| Resistance | Opposition to current flow, measured in ohms (Ω). |
| Circuit | A closed loop through which electric current can flow. |
? Quick check
Try to answer before you tap. Answers are hidden underneath.
A component has a voltage of 12 V across it and a current of 3 A through it. Find its resistance.
4 Ω (using R = V ÷ I = 12 V ÷ 3 A = 4 Ω).
In a series circuit with two lamps, one lamp breaks. What happens to the other lamp?
It also turns off, because a series circuit is a single loop — a break anywhere stops all current.
Why are household circuits wired in parallel rather than series?
So that each appliance gets the full voltage and works independently — if one device is switched off or breaks, the others keep working.