Simple circuits · Grade 6
A circuit is a complete loop that electricity can flow around. A cell or battery pushes the electricity, wires carry it, and components such as bulbs, buzzers and motors use it. If there is a gap anywhere in the loop, nothing works – that is exactly how a switch turns things on and off.
Key facts
- Electricity only flows round a complete loop with no gaps.
- A switch makes (closed) or breaks (open) a gap in the loop.
- Cells joined in a row, the same way round, add their voltages: two 1.5 V cells give 3 V.
- More cells for each bulb makes the bulbs brighter; more bulbs in one loop makes them dimmer.
- Circuit symbols: a cell is a long and a short line; a bulb is a circle with a cross; a switch is a gap with a lever.
- A bulb works best at the voltage marked on it; too much voltage can blow it.
Worked examples
Example 1
A torch needs 4.5 V. How many 1.5 V cells must be put in a row?
Answer: 3 cells