ELECTRICAL SYSTEM
Questions:
1. Where does electricity come from?
2. What are the sources of electricity?
3. Do I know how to connect bulb(s) to
battery/batteries correctly?
4. Do I know the symbols for each of the
electrical components?
ELECTRICAL SYSTEM
5. What is a series circuit?
6. What is a parallel circuit?
7. Do I know how to draw a circuit diagram
accurately?
8. Am I able to observe & compare different
circuits and identify the variables changed?
9. What affects the brightness or current
flowing through a bulb?
ELECTRICAL SYSTEM
10. What are electrical conductors and
insulators?
11. Do I know how to use electricity safely?
12. What are some ways to conserve
electricity?
The Electric Bulb
Series / Parallel?
Series / Parallel?
Compare
What Affects the Brightness /
Current Flowing through a Bulb?
More batteries  Higher current  Brighter bulb
What kind of arrangement?
Batteries arranged in series.
What Affects the Brightness /
Current Flowing through a Bulb?
More bulbs  Lower current  Dimmer bulbs
What kind of arrangement?
Bulbs arranged in series.
What Affects the Brightness /
Current Flowing through a Bulb?
More bulbs  Same current  Same brightness of bulbs
What kind of arrangement?
Bulbs arranged in parallel.
Is it true…
•
… the second bulb is less bright than the first
bulb in a series circuit because electric
current has been ‘used up’ by the first bulb in
the circuit?
•
… in an open circuit, electric current flows to
the part where there is a gap and ‘turns back’
to the battery as it cannot flow across the
gap?
1. The diagram below shows a circuit and what
happens to the lamp when three rods, A, B
and C are placed, one at a time, across PQ.
From the results, which rod is most likely to be
a conductor of electricity? Give a reason. (1m)
Key Word(s): conductor of electricity,
reason
Answer: Rod B. As the bulb lights up, this
means that Rod B allows electricity to pass
through it, forming a closed circuit.
In another experiment, some wax was placed
on the top end of the same three rods, A, B and
C. The three rods were then placed on top of a
hot surface as shown below. It was observed
that the wax on rod B melted first, followed by
that on rod C and then rod A.
(b) What conclusion can you draw about the
conduction of heat in rods A, B and C? (1m)
Key Word(s): conduction of heat in A, B & C
Answer: Rod B conducts heat the fastest,
followed by rod C and finally rod A.
(c) From your answers to (a) and (b), what can
you conclude about the likely relationship
between a conductor of electricity and a
conductor of heat? (1m)
Key Word(s): *relationship between
conductor of electricity & conductor of heat
(*relationship: Order is important)
Answer: A material which is a conductor of
electricity is also a good conductor of heat.
2. (a) In the circuits P and Q below, all the
bulbs are lit.
In the table below, write down the number
of bulbs that would remain lit when one of
the bulbs in each circuit is blown.
Key Word(s): number of bulbs, remain
lit, one bulb is blown
Skill(s): Observe & Compare the
circuits
Variable changed: Arrangement of
bulbs
Answer: Circuit P – 3, Circuit Q - 2
(b) In circuit R below, all the bulbs B1, B2, B3 and
B4 are lit.
Write down the smallest number and the largest
number of bulbs that would remain lit when
one of the bulbs in circuit R is blown.
Give a reason for your answer. (2m)
Highlight key word(s).
Highlight paths of electric current.
(i) Smallest number of bulbs remaining lit: 0
Reason: When bulb B1 or B4 is blown, the
circuit is open.
(ii) Largest number of bulbs remaining lit: 3
Reason: When B2 or B3 is blown, electricity
can still pass through another path, there will
still be a closed circuit.
3. Samy set up an experiment as shown
below.
When the metal clips were connected to
the container, the bulb lit up.
State whether liquid P and material Q must
be conductor(s) of electricity.
Give a reason for your answer.
Skill(s): Observe the diagram
Highlight key word(s) in the question &
on the diagram.
Key Concepts: close / open circuit
3. Samy set up an experiment as shown below.
When the metal clips were connected to the
container, the bulb lit up.
State whether liquid P and material Q must be
conductor(s) of electricity.
Give a reason for your answer.
Answer: Liquid P – No. The metal clips are not
connected to liquid P. The electricity does not
need to pass through liquid P.
Material Q – Yes. The metal clips are
connected to material Q, so it must be a
conductor of electricity to close the circuit / to
allow electricity to pass through it.
4 (a) Andrea wants a light bulb to light up
when her toy train is pushed through a
tunnel. She makes an electric circuit for
her toy train. Andrea makes a tunnel and
puts a strip of foil inside the tunnel roof.
The picture shows Andrea’s tunnel and
the wiring on her train.
The foil strips on the train act like a switch.
When both foil strips on the train touch the
foil inside the tunnel roof, the bulb lights up.
Complete the circuit diagram below by
drawing the switch and the bulb to show
the circuit on Andrea’s train. (2m)
Give ONE property of metal foil which makes it
a good material for Andrea to use as a switch.
(1m)
It is an electrical conductor. / It is flexible.
When only one foil strip on the train is touching
the foil in the tunnel, the bulb does not light
up.Complete the sentence to explain why the
bulb does not light up. (1m)
The circuit is open. / The circuit is not closed.
(d) The bulb on the train only lights up when all
of the train is inside the tunnel. Andrea
wants to improve her circuit so the bulb
lights up when the train has only just
entered the tunnel.
Which train has foil strips that would allow
the bulb to light up when the train has only
just entered the tunnel? (1m)
Answer: Top right