Page 158 - Science Coursebook

10.9 Components in parallel

We have seen that, when two lamps are connected in
series to a single cell, they are dim. This is because the
current in the circuit is small.

It is more difficult for the electrons to flow round the

circuit than if there was only one lamp. Two lamps
have more resistance than one lamp.
There is another way to connect two lamps to a cell.
Place them side by side, as shown in the photograph.
You can see that both lamps shine brightly.
These two lamps are connected in parallel.
When components are connected side by side in this
way, we say they are in parallel with each other.

Parallel diagrams
The circuit diagram shows how we represent the circuit
with two lamps connected in parallel.
If you look closely, you will see that each of the two −
lamps has one end connected directly to the positive +
end of the cell, and the other end connected directly to
the negative end.
Each lamp feels the full push of the cell and so it lights
up brightly. Circuit diagram to show two lamps
connected in parallel.
To remember the difference between series

and parallel:
• ‘in series’ means ‘connected end-to-end’
• ‘in parallel’ means ‘connected side by side’.

Activity 10.9

Parallel connections

SE 1 Set up a circuit with a single cell and a single lamp.
2 Connect a second lamp in parallel with the first.

3 Draw a circuit diagram to show your parallel circuit. Make a note of how

bright your lamps are. Does the brightness of the first lamp change when you
add the second?
4 Now repeat steps 1 and 2, this time including an ammeter in the circuit next
to the cell to measure the current flowing from the cell. Make a prediction:

how will the current change when you add the second lamp?
5 Draw a diagram to represent the circuit with the ammeter. Make a note of
the value of the current in the circuit when there is one lamp, and when there
are two.

156 10 Electricity

A+I A+E