Page 156 - Science Coursebook

10.8 Changing circuits 2

Adding more cells to a series circuit increases the
voltage and so the current is bigger. What happens
if we add other components to a series circuit?

In topic 10.5 you saw what happens if two lamps
are used in series instead of one. The lamps are
both dim (not bright). The photograph shows this.

Question
A+I 1 How could you change the circuit to make
the lamps brighter? Explain your answer.

One after another
By thinking about the electrons in the circuit, we can understand why the current is
smaller when there are two lamps in the series circuit.
The electrons are being pushed by the cell. It has to push them through one lamp and
then through the next.
It is easier for the cell to push the electrons through one lamp than through two, and
so the current is bigger when there is only one lamp in the circuit.

Electrical resistance
We say that a lamp has resistance. The more resistance there is in the circuit, the
harder it is for the cells to push the electrons round, and so the current is smaller.
The pictures show some other components which have resistance.

A resistor is used to make the A variable resistor allows you to A buzzer makes a sound when
current smaller in a circuit. control the amount of current in the current flows through it.
a circuit.

154 10 Electricity

A+E