Series and Parallel Circuits

In this section we will look at how batteries, switches and
lamps can be connected in either series or parallel. To help
us do this we will use a "multimeter" to see what is happening
to the voltages inside the circuits.

To begin, you will need to find out how to measure
voltage with a multimeter:-

Open the "using a multimeter" link at the top of this screen
and carefully read sections 1 and 2. Then read the part
headed "Measuring Voltage" before continuing.

The multimeter below has had its centre dial turned round to
read up to 20 Volts. We can now use it to check the voltage
(potential difference) across the two terminals of our single
battery.

 

Move the battery
between the
meter's red (+) and
black (-) probes.
The meter will
then display the
voltage of the
battery.

 

 

 

 

 

 

Q17, The voltage on the + side of the battery is
measured on the red probe at 1.5volts. Is this higher
(more positive) or lower (more negative) than the zero
voltage on the - side of the battery?

Higher (more positive)
Lower (more negative)

 

 

Batteries
in Series

If the batteries are
connected as shown so that
the + side of one connects
to the - side of the other
then the total voltage is :-

1.5 volts + 1.5 volts

= 3 volts.

Torches often have two or
more batteries in series to
increase their power.

Q18, If four 1.5 volt batteries were connected together
in series what would the total voltage be?

1.5 volts
3.0 volts
6.0 volts
5.5 volts

 

 

Batteries
in Parallel

In this arrangement the +
side and - side of each
battery is connected
together so that the
combined voltage remains
at 1.5 volts.

Batteries connected in
parallel, like this, can
provide more power than
a single battery. This is
because they are able to
provide twice the current.

 

Q19, A portable radio uses six 1.5 batteries. Three of
these batteries are connected in series. The other three
are also connected to each other in series. These two
sets of three are then connected to each other in
parallel. What is the combined final voltage of these six
batteries?

(Hint: Draw the battery arrangement on paper first).

Please answer in the text box below.

volts

 

Switches in
Series

 

 

The slider
switches in this
circuit are "on",
when they are
put to the "1"
position.

Click the
switches to
make the light
work.

 

Switches in
Parallel

 

Try clicking the
switches again
to see if both
have to be on
for the light to
work.

 

 

Q20, Click against the statements that are true about
series and parallel circuits.


Switches in series have to both be on for current
to pass.
Switches in series pass current when only one is
on.
Switches in parallel have to both be on for current
to pass.
Switches in parallel pass current when only one is
on.

If we connect output
devices such as lamps in
series, we will share the
available voltage
between them. This
could mean the lamps
will not glow so brightly
unless they are replaced
with lower voltage
types.

Lamps
in
Series

In this circuit the voltage
seen across each of the
identical lamps is half
the battery voltage
.

 

If we connect output devices in parallel we do not notice any drop in voltage. This is the case if the battery has enough power. Each lamp glows as brightly as if it were connected to the battery on its own.

Lamps
in
Parallel

In this circuit the voltage seen across each of the identical lamps is the same as the battery voltage.

We dont get extra power for nothing though, as the current from the battery must have doubled - see below.

 

Power (from battery) = Current x Voltage


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