STARTER
Draw a circuit diagram for this circuit
AIM
•
Explain the difference between series and parallel circuits
•
Describe some of the benefits of parallel circuits
SPOT THE DIFFERENCE
What is different?
WHAT IS A SERIES CIRCUIT?
This is a simple series circuit.
In 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.
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
MODELLING PARALLEL CIRCUITS
INVESTIGATE
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.
WHAT HAPPENS WHEN YOU ADD MORE BULBS?
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
SERIES AND PARALLEL
Are these circuits series or parallel?
A
+ -
B
+ -
C
+ -
D
E
+ -
+ -
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
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.
-
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.
+
-
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.
PLENARY