Circuit diagrams

LI: I am learning to read circuit diagrams.

SC: I can name circuit symbols · I can tell series from parallel · I can say where an ammeter and a voltmeter go.

1.Match each symbol to its name.

Drag each symbol onto its name, or tap a symbol and then its name.

Hint

A cell has one long line and one short, thick line. A battery is more than one cell joined together, so look for more lines.

A battery is two or more cells joined together. On a cell, the long thin line is the positive (+) side.

2.Spot the mistake: this lamp won't light. Why not?

The open switch leaves a gap. Current only flows round a complete loop.

3.Circuit A is…

Hint

Put your finger on the cell and follow the wire. If there is only one path all the way round, it is series. If the wire splits (look for dots), it is parallel.

There is only one loop, so the current goes through both lamps, one after the other.

4.Circuit B is…

The wire splits at the dots, so each lamp is on its own branch.

5.Circuit C is…

Hint

Don’t be fooled by where the lamps are drawn. Follow the wire from the cell: does it ever split into two paths?

One lamp is on the side, but there's still only one loop. The wire never splits.

6.Circuit D is…

Hint

Start at the top of the cell and follow the wire. When you reach a dot, can the current go two different ways?

The lamps are drawn upright, but each one has its own path from the cell and back.

7.In this circuit, lamp X breaks. What happens to lamp Y?

Hint

Imagine lamp X has been taken out. Can you still trace a complete loop from the cell, through lamp Y, and back to the cell?

It's still in a complete loop with the cell, so it stays lit.

8.Why are the lights and sockets in a house wired in parallel?

Each appliance is on its own branch: you can switch it on and off by itself, and one fault doesn't turn everything off.

9.Which circuit correctly measures the current through the lamp?

Hint

Look at the letter in each circle: A is an ammeter and V is a voltmeter. To measure current, the current has to flow through the meter.

An ammeter (A) measures current. It goes in series: in the loop, so the current flows through it.

10.Ammeter P reads 0.25 A. What does ammeter Q read?

Hint

Follow the loop from the cell. Is there anywhere else the current could go, apart from through P, the lamp and Q?

In a series circuit the current is the same everywhere. Current isn't used up: the lamp takes energy, not current.

11.How should a voltmeter be connected to measure the voltage across a lamp?

A voltmeter (V) goes in parallel: across the component, one wire on each side.

Challenge12.The two lamps are identical. Ammeter X reads 0.6 A. What does ammeter Y read?

Hint

At the dot, the current from the cell splits between the branches. How many branches are there, and are the lamps the same?

In a parallel circuit the current splits between the branches. The lamps are identical, so each branch gets half: 0.6 A ÷ 2 = 0.3 A. The branch currents add up to the current from the cell.