Using Electricity in Different Ways
The brightness of a bulb depends on the amount of electrical current flowing through the circuit.
The amount of electric current that is able to flow through the bulbs in a circuit is affected by
some ways.
1 Increasing The Number Of Batteries In Series
We can adjust the brightness of a bulb in a circuit by increasing or decreasing the number of
batteries used.
To make the bulb light up more brightly, we place more batteries in the electrical circuit. The
batteries should be arranged in a series, meaning the positive terminal of one battery touches
the negative terminal of another battery. This will increase the amount of electric current flowing
through the circuit.
The bulb is bright when
one battery is used.
The bulb is brighter when
two batteries are used.
The bulb is brightest when
three batteries are used.
Batteries connected in a series
Alternatively, to make the bulb light up less brightly, we place fewer batteries in the electrical
circuit. The electric current flowing through the circuit decreases, so the bulb does not light up
as brightly as before.
However, the bulb will blow when we keep increasing the number of batteries in a circuit.
This happens because there is too much electrical current flowing through the circuit. The
voltage of the bulb cannot handle the increase in electrical current and the bulb fuses.
2 Increasing The Number Of Bulbs In Series
For bulbs arranged in series in a circuit with a fixed number of batteries, the greater the number
of bulbs, the dimmer each of the bulbs will be as the electric current has to be shared between
all the bulbs. If one bulb fuses, there will be a gap in the circuit and all the other bulbs will not
light up.
The brightness of a bulb is compromised when there are many bulbs in a series.
Adapted:
PSLE Science Partner A Complete Guide to L&U Block
© Singapore Asia Publishers Pte Ltd. All rights reserved.
Reproducible for home/classroom use only.
STRICTLY NOT FOR SALE.
Look for other useful resources: www.sapgrp.com
Book 1.indb 11
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10/12/2016 10:45:35 AM
3 Arrangement Of Bulbs In Series And In Parallel
When we change the arrangement of the bulbs in a circuit, the brightness of the bulbs will be
affected.
When two bulbs are connected in series, there is only one path for electricity to flow through
the two bulbs. The amount of electric current that is able to cross each device depends on
its resistance of each device and the current flowing through the circuit. When adding more
components in a series circuit, the current flow decreases. Therefore, the bulbs light up but not
so brightly.
A series circuit with one battery and two bulbs
In a series circuit, if a bulb fuses or a component is disconnected or damaged, there is a gap in
the circuit. It becomes an open circuit, disrupting the flow of electric current.
In a parallel circuit, all the components have access to the full amount of electrical current
available. If any one of the components of a parallel circuit stops working, the other components
will still be able to carry on working. The bulbs stay bright even if more bulbs are added in
parallel.
In a parallel circuit, each bulb is directly connected to the power source. Therefore, the bulbs
arranged in parallel light up more brightly than when they are arranged in series.
A parallel circuit with one battery and two bulbs
4 Arrangement Of Batteries Connected In Parallel
When the batteries are arranged in parallel, the bulbs in all three circuits will be of the same
brightness. This is because the current flows through one loop at a time until the chemical potential
in the battery has been used up before flowing through the next loop to make use of current from the
second battery.
same brightness
same brightness
same brightness
Batteries connected in a parallel
However, the bulb in the third circuit shown above will remain lit three times as long as the bulb
in the first circuit because it has three batteries to obtain its power from.
Adapted:
PSLE Science Partner A Complete Guide to L&U Block
© Singapore Asia Publishers Pte Ltd. All rights reserved.
Reproducible for home/classroom use only.
STRICTLY NOT FOR SALE.
Look for other useful resources: www.sapgrp.com
Book 1.indb 12
2
10/12/2016 10:45:35 AM