This document provides information about series and parallel circuits: 1. It explains that a series circuit has one continuous loop with no points for current to split or join, while a parallel circuit has at least one junction where current can split and join across multiple paths. 2. Guidelines are given for measuring current and voltage in series and parallel circuits. Current is the same everywhere in a series circuit but splits across components in a parallel circuit. Voltage is shared across components in series but is the same across parallel components. 3. Energy is transferred but not created or destroyed in circuits. Chemical energy from batteries is converted to electrical and then other forms like light and heat, with efficiency calculated as useful output energy over total

1. Target
To know how to set up a series
circuit
Electricity
Thursday 9 February 2017

2. A circuit is like a central heating
system in a house:
Boiler
and
pump
radiator
High pressurelow pressure
There is a pump that
pushes water round
the system. The water
everywhere starts to
move AT THE SAME
TIME.
There are pipes that
CARRY the water.
In the pipes the water
is FLOWING.
flow of
water

3. An electrical circuit is very similar to a central
heating system.
The bulb in the circuit is like a radiator. An electrical
device uses electrical energy supplied by the circuit.
Instead of a flow
of water,
electricity flows in
an electrical
circuit.
The wires are like
pipes; they carry
the electricity
(called current)
round the circuit.
The electrical current is pushed by the battery, which has the
same function as the pump and boiler.
The strength of push provided by the battery is called its voltage.

4. lamps
This is a simple series circuit. In a simple
series circuit, everything is connected in one
loop across the terminals of the battery. So
there AREN’T any 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.
Series circuit

5. Here are some other simple series circuits:
1. Two resistances (resistors) connected in series.
2. A rheostat (or variable resistor) and a bulb connected in series.
R1 R2
Series circuit

6. The unit of measure for current is the "amp" which
has the symbol A.
We measure the current using a device called an
ammeter. In a circuit this is given the symbol
When measuring the current through a
component, the ammeter is always connected in
series (in the same loop) with that component.
AA
A
Measuring current

7. When measuring the voltage across a component, the
voltmeter is always connected in parallel with (or across)
the component.
V3
V2
V1
We measure the voltage using a device called an
voltmeter. In a circuit this is given the symbol V
The voltage supplied by the battery is shared between all
the components in a series circuit.
This is still
a SERIES circuit.
Measuring voltage

8. Series circuit

9. A
V
component
here
R
Voltage is measured by connecting the voltmeter across
(or in parallel with) the component.
Voltage is measured in volts and the symbol for this is V.
V
Components
Measuring voltage - across a resistance or
a bulb

10. 1. Set up the circuit as shown above.
2. Connect the voltmeter across the power supply and
measure the supply voltage.
3. Then connect the voltmeter across the resistance (R)
and measure this voltage.
Experiment: measuring voltage
R
V
V
Circuit 1

11. 1. Add another resistance (R2) to the circuit as shown.
2. Connect the voltmeter across the power supply and
measure the supply voltage.
3. Then measure the voltage across each of the resistances.
R1 R2
V
V1 V2
Circuit 2
Experiment: measuring voltage

12. Record your results:
Circuit 1: Voltage (supply) = V
Voltage (R1) = V
Circuit 2: Voltage (supply) = V
Voltage (R1) = V
Voltage (R2) = V
R1 R2
V
V1 V2
R1
V
V
Circuit 1 Circuit2

13. The current is the ____ of electricity around the circuit. The
_______ is the amount of push.
When two components were put into Circuit 2, the voltage
of the supply was the ____ as Circuit 1. However, the
voltage across R1 ________ .
The voltage across both components in circuit 2 added to
be equal to the _____ voltage.
supply, decreased, voltage, flow, same
Circuit2
R1 R2
V
V1 V2
R1
V
V
Circuit 1 Circuit2

14. V1
V2
V3
Measuring voltage in parallel circuits
Connect together the circuit shown above and
measure, in turn, the voltage at V1, V2 and V3.

15. Write down your results in the table below :
Voltmeter Voltage
(V)
V1
V2
V3
Explain anything you notice about the results.

16. Target
To know how to set up a parallel
circuit
Electricity
Thursday, February 9, 2017

18. Parallel circuits

19. Parallel and series circuits

20. Experiment: measuring current
R1
1
2
A
1. Set up the circuit as shown above.
2. Measure the current using the ammeter at positions
1 and 2.
Circuit 1
A

21. R1 R2
1
2
3
A
A
A
1. Add another resistor into the circuit.
2. Now measure the current using the ammeter at
positions 1, 2 and 3.
Circuit 2
Experiment: measuring current

22. Results
Current Position 1
Current Position 2
Current Position 3
Current Position 1
Current Position 2
Circuit 1
Circuit 2

23. Circuit 1
The current at different positions in the circuit, before and
after the resistor, was the _____.
Current is ___ used up by the components in the circuit.
Circuit 2
Increasing the number of components in the circuit
_______ the current.
The current at all points in a series circuit is the ____.
same / same / decreased / not
Conclusions

24. 1. Set up the circuit as shown above.
2. Connect the voltmeter across the power supply and
measure the supply voltage. Then measure the
voltage across the resistance. Measure the current.
Experiment: cells
R1
V
V
Circuit 1
A

25. 1. Add an additional battery to the circuit.
2. Connect the voltmeter across the power supply and
measure the supply voltage. Then measure the
voltage across the resistance. Measure the current.
R1
V
V
Circuit 2
A
Experiment: cells

26. Results
Circuit 1: one battery
Circuit 2: two batteries
Supply Voltage
Voltage R1
Current
Supply Voltage
Voltage R1
Current

27. Delete the wrong answer:
Increasing the number of batteries / cells
increases/decreases the current that flows in the circuit.
The current/voltage depends on the current/voltage.
Conclusions

28. 1. In a series circuit the current is the same at
any point in the circuit.
2. The supply voltage is shared between the
components in a series circuit.
3. The current depends on the voltage in ANY
circuit.
Summary for series circuits

29. Parallel circuits
A parallel circuit is one which 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

30. Measuring current in parallel circuits
A1
A2
A3
A41 2
3
4
1. Place the
ammeter, in turn,
at positions 1, 2, 3
and 4.
2. Record the
ammeter reading
at the points in the
table shown.
Ammeter Current (A)
A1
A2
A3
A4

31. For a parallel circuit, the current that leaves the cell or
battery is the same as the current that returns to the
cell or battery. The current does NOT get used up by
a circuit, just the energy the electrons are carrying.
A1 = A4
The current splits up at the first junction and then joins
together at the second junction. If the bulbs are
identical then the current will split evenly. If the bulbs
are NOT identical, then the current will NOT split
evenly. The following is always true for this circuit.
A1 = A2 + A3 =A4

32. Energy in circuits
This section deals with the energy transfers in electric
circuits.
The most important thing to understand about energy is
that it cannot be created or destroyed.
In all devices and machines, energy is transferred from
one type to another.

33. lamps
When this circuit is connected, chemical energy
stored in the battery is transferred via electrical
energy to heat and light energy in the bulbs.
The total amount of heat and light energy is the
same as the amount of chemical energy lost
from the battery.
Energy transfer in electrical circuits

34. Notice, most of the energy from the battery
does not produce light - most of it is wasted as
heat!
chemical energy
lost from battery
(e.g. 100J)
heat energy of bulb95 J transferred to
5J transferred to bulb as
light energy
Energy transfer in electrical circuits

35. Energy efficiency
We can work out the efficiency of an energy transfer:
x 100
For this bulb
efficiency = (5/100) x 100 = 5%
total energy input
useful energy output
%Efficiency =

36. Other energy transfers
Batteries can power many things -
What sort of energy is the electrical energy
transferred into in these examples?