Why do we need parallel circuits?
04/09/2016
Parallel Circuits
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Parallel or
series?
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Starter
• Draw a circuit diagram for this circuit
Where do we see “parallel” in every day situations?
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Starter
• Draw a circuit diagram for this circuit
• Add an ammeter to measure the current through
the three lamps
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Aim
• Explain the difference between series and parallel
circuits
• Describe some of the benefits of parallel circuits
Key words
• Series circuit 직렬회로
• Parallel circuit 병렬회로
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Have you ever wondered?
Why do we have series and parallel circuits?
The bigger
picture
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Spot the difference
• Can you draw the
diagram for each?
• What is different?
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What is a series circuit?
This is a simple series circuit.
Everything is connected in one loop across the
terminals of the battery.
There are no points where the current can split
or join (these are called junctions).
This circuit has two lamps connected in series.
Circuits are always drawn using straight lines.
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What is a parallel circuit?
A parallel circuit is one that contains a point (a junction)
where the current can split (point A) or join (point B).
This means that there is more than one path around the
circuit.
A
B
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Modelling parallel circuits
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Investigate
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What happens when bulb X breaks?
• If one bulb ‘blows’, or is
taken out of its holder, the
other bulbs still light.
• You can switch the bulbs on
and off independently.
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What happens when you add more bulbs?
• Each bulb in a parallel circuit
forms a complete circuit
with the cells
• This means two light bulbs
light to the same brightness
as one
• If you add more bulbs, the
brightness of all stays the
same
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Series and parallel
• A series circuit has one path for the current to
take (just one
loop).
+
+
A
A
• A parallel circuit has more than one path for
the current to take (two or more loops).
+ -
+ -
A
A
A
A
A
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Series and parallel
• Are these circuits series or parallel?
A
+ -
B
+ -
C
+ -
D
E
+ -
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+ -
Fairy lights –+ a series circuit
-
If one bulb breaks or is removed the circuit is no
longer complete so all of the bulbs will go out.
+ -
break
in the circuit
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Classroom light – a parallel circuit
+
-
+
If one bulb breaks or is
removed the current can
still take the other paths
so the other bulbs will
stay lit.
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-
Switches in parallel circuits
• In fact the classroom lights have more than one bulb on each path
plus a switch.
• This allows us to turn each path of light on and off independently.
+
-
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1. What happens when we add
bulb Z to the circuit?
2. In this circuit, which bulb or
bulbs will light up if you close
switches A and C?
3. Which bulb or bulbs will light up
if you close switches B and C?
4. Do you think the lights in your
house are wired in series or in
parallel? Explain your choice.
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Plenary
Key words
• Series circuit – only has one path for the electrons.
If you add more bulbs, the light gets dimmer. If one
bulb breaks, the hole circuit goes out. The voltage is
shared between the bulbs
• Parallel circuit – has different branches for the
electrons to travel. If you add more bulbs in parallel,
all have the same brightness, because each bulb has
full voltage from the battery. If one bulb breaks, the
others still work
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