Series and Parallel Circuits 

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

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

Open the "Using a Multimeter" link at the top of the screen
and read about voltage measurement under "Connecting Up". You may be interested to read the other sections there too.

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
the + side of one connects
to the - side of the other),
then the total voltage is :

1.5 volts + 1.5 volts

= 3 volts.

 

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.

Two batteries connected in
parallel 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 volt 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 this arrangement of six 1.5 volt batteries?

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

Please answer in the text box below.

volts

 

 

Switches in
Series

 

 

The slider switches in these circuits are closed, "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, For the series and parallel circuits above - Select the statements below that are true.


Switches in series have to both be switched on (closed), for current to pass in the circuit.
Switches in series pass current in the circuit when only one is switched on (closed).
Switches in parallel have to both be switched on (closed), for current to pass in the circuit.
Switches in parallel pass current in the circuit when only one is switched on (closed).

 

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

Lamps
in
Series

In this circuit, the actual voltage (as seen across each of the identical lamps), is now only half the battery voltage.

 

If we connect output devices in parallel we don't notice any drop in voltage. Each lamp glows as brightly as if it were connected to the battery on its own. (However that's only true if the battery can provide the extra power needed).

Lamps
in
Parallel


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

Power In a Circuit

The above circuit does not give us this extra power for nothing. The current from the battery will need to double for both light bulbs to shine at full brightness. This means the power used from the battery will need to double.This can be seen from the power equation you were introduced to earlier:

Power in Watts(W) = Current(I) x Voltage(V)

For this equation to be true: If the voltage of the battery stays the same and the current on the right side doubles (for both bulbs to be fully lit), the power on the left side will need to double as well. In practice we have seen in Section 3 ("Ohms Law"), how different batteries have different amounts of available current or power. This is due to a battery's "internal resistance" limiting the current that is available.


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