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1. FUNDAMENTAL Physics – Circuits: 3.3 Series and Parallel Circuits
Series Circuit
Learning Outcomes
• I can distinguish between series and parallel circuits
• I can describe how current passes around series and parallel circuits
• I can describe how voltages is shared our in series and parallel circuits
• I know what type of circuit is best for domestic
appliances such as lighting
Series Circuits
This is a series circuit because there is only …one…. possible path for
the current.
Readings:
I1 = …0.31.. A I2 = .0.31.. A I3 = …0.31.. A
Conclusion about Current
In a series circuit the current is the same all round the circuit.
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A1
A2
A3
Safety. Avoid an
overheated circuit. Use
PD max of 6V

2. FUNDAMENTAL Physics – Circuits: 3.3 Series and Parallel Circuits
Potential Difference (p.d.) in a Series Circuit
At a very simple level the Potential Difference is the …electrons…
that makes the charges move.
Readings
V1 = …5.44. V V2 = 2.61…. V V3 = 2.75… V
Conclusion about Potential Difference in a Series Circuit
In a series circuit the potential difference is …Shared… …… .
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V1
V2 V3

3. FUNDAMENTAL Physics – Circuits: 3.3 Series and Parallel Circuits
Adding a Third Lamp
Adding Lamps in Series
When we add more lamps in a series circuit we observe that the
lamps become DIMMER
Why is this?
More energy being used and more resistance
Simple explanation:
• adding more lamps increases the …resistance….. which …
lowers….. the current .
• less current means the lamps are …dimmer…… .
or
‘A*’ Explanation
• adding more lamps will …share…. the POTENTIAL
DIFERENCE between more lamps and
• each lamp gets a …smaller….. share of the potential
difference.
• which means each lamp is receiving less …energy…. for
every Coulomb of charge,
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A1
A2
A3
V1
V2
V3
V4
A4

4. FUNDAMENTAL Physics – Circuits: 3.3 Series and Parallel Circuits
• so the lamps are …dimmer…….
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5. FUNDAMENTAL Physics – Circuits: 3.3 Series and Parallel Circuits
Parallel Circuits
This is a parallel circuit because there is more than one possible route
for the current. There are junctions!
There are three main advantages with a parallel circuit:
• If one component breaks the other components can still work,
because they are still part of a …parallel….. Circuit. The
electrical components in our homes are arranged in a special
PARALLEL circuit, called a LOOP circuit.
• If you add extra components (lamps) in parallel, all the lamps
are fully bright.
• Individual lamps can be switched on and off independently.
For these reasons, domestic (household)) electrical circuits, such
as domestic lighting, are wired in ……parallel circuits……
(called ring circuits).
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Safety.
Careful with overheated
circuit. Keep PD max of
6V

6. FUNDAMENTAL Physics – Circuits: 3.3 Series and Parallel Circuits
Current in a Parallel Circuit
Readings:
I1 = …0.84… A I2 = …0.40…. A
I3 = …0.43... A I4 = …0.85… A
Parallel Current Conclusion
In a parallel circuit the current is …split….. at the first junction
and then …combines..… at the second junction.
This is actually Kirchoff’s First Law:
• The current arriving at a junction is the same as the current
leaving the junction.
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A1
A2
A3
A4

7. FUNDAMENTAL Physics – Circuits: 3.3 Series and Parallel Circuits
Potential Difference in a Parallel Circuit
Readings:
V1 = ...4.44… V V2 = …4.19… V V3 = …4.29… V
Parallel Potential Difference Conclusion
• In a parallel circuit the potential difference is the …same….
• All lamps are fully …lit…..
• All lamps receive the full …energy… from the battery.
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V1
V2
V3

8. FUNDAMENTAL Physics – Circuits: 3.3 Series and Parallel Circuits
Extension Circuit 1.
Measure the current and voltages at key places in this circuit. What
can you conclude?
More energy used and also more resistance so the energy is not shared
with all the bulbs equally due to different resistance of each bulb.
Extension Circuit 2.
Measure the current and voltages at key places in this circuit. What
can you conclude?
Homework; P 187, Q 1-4
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