Page 150 - Science Coursebook

10.5 Electric current in a circuit

A lamp can show us when there is an electric current in
a circuit.
• If the lamp lights up, there is a current.
• A brighter lamp shows a bigger current.
The photograph shows a very simple circuit. A lamp is
connected to a cell. You can see that the lamp is shining,
showing that an electric current is flowing through it. An electric current makes the lamp light up.

Activity 10.5A

Connecting lamps in series

SE You can use a cell to light up two lamps. The circuit diagram
shows how to do this.
1 Before you try this, make a prediction. How bright will the
lamps be? Will they both be equally bright, or will one be
brighter than the other?
Try to give an explanation for your prediction. Discuss
your ideas with a partner, and then present them to the
rest of the class.
2 Build the circuit and test your ideas. Do you need to
change your ideas?
3 Predict what you will observe if you make a circuit with
three lamps, all in a row. Test your prediction. A circuit with a cell, a switch and

When you have learnt more about electric currents, you will two lamps.
have a better understanding of this experiment.

Measuring electric current
We can measure the current in a A
circuit using an instrument called An ammeter
an ammeter.
circuit symbol.
The unit of electric current is the
amp (symbol A).

To connect an ammeter in a circuit,
it is necessary to make a break in the
circuit. Then the current can flow

through the ammeter.

Adding an ammeter to a circuit.

148 10 Electricity

A+I A+E