1Measuring current
Current is measured in amps (A) with an ammeter. It goes in the loop, in series, so the current flows through it.
ampammeterseries
Lesson 6.2 notes
Current in series and parallel circuits
Measuring current with an ammeter, and how current behaves in series circuits and in parallel branches.
2The same all the way round
In a series circuit the current is the same everywhere. The lamp doesn't use up any current: the same amount flows back to the cell.
3Series circuits
In a series circuit everything is on one loop. Add more lamps and the current gets smaller, so every lamp is dimmer.
series circuit
4One breaks, all go out
If one lamp in a series circuit breaks, there is a gap in the only loop, so all the lamps go out.
5Parallel circuits
In a parallel circuit each lamp is on its own branch. Each lamp gets the full push of the cell, so adding lamps doesn't make them dimmer.
parallel circuit
6Currents add up
At a junction the current splits between the branches, then joins up again. The branch currents add up to the current from the cell: 0.2 A + 0.3 A = 0.5 A.
junction
7Parallel at home
Lights and sockets at home are wired in parallel. Each can be switched on and off by itself, and one broken bulb doesn't put out the rest.
Explore: Series and parallel lab
Build a series or a parallel circuit, add lamps and break one. Watch the ammeters and how bright the lamps are.
Common mistake: A lamp doesn't use up current
The same current flows back to the cell as leaves it. The lamp transfers energy, not current. That's why every ammeter in a series circuit gives the same reading.
Remember
- An ammeter measures current in amps. It goes in series, so the current flows through it.
- Series: one loop, so the current is the same everywhere. More lamps make the current smaller.
- Parallel: separate branches. The branch currents add up to the current from the cell.
Going further at GCSE