Page 151 - Science Coursebook

10.5 Electric current in a circuit

Activity 10.5B
Measuring current around a circuit

SE Now you can find out more about the current in
a circuit.
1 Set up a circuit with a cell and two lamps, as + −
before. You should find that the two lamps

are equally bright.
2 Connect an ammeter as shown at position 1 A
in the circuit. Note the value of the current. position 1 position 3
3 Repeat with the ammeter at position 2, and
then at position 3.
4 Discuss whether your results agree with what position 2
you found when you used lamps instead of
an ammeter.

Current in a series circuit
In the experiments in this topic, you should have found that
the current is the same all the way round each circuit.
+ −
We picture the current coming from the positive end of the
cell. It flows round the circuit, through the ammeter, one lamp

and then through the next. A

It then flows back to the negative end of the cell. It doesn’t get
used up as it goes through the lamps.
A circuit like this, where the components are connected end-
to-end, is called a series circuit. The current flows through The current, shown by the blue

the components one after another. The current is the same all arrows, is the same all the way
the way round a series circuit. round a series circuit like this.

Questions
1 Does the electric current get used up as it goes round an electric circuit?
2 In a series circuit, an ammeter shows that the current leaving the positive end

of a cell is 0.5 A. What current flows into the negative end of the cell?

Summary
• A circuit with all the components connected end-to-end is called a
series circuit.
• The current is the same all the way round a series circuit.

10 Electricity 149