Credit to original creator

1. Electricity
Part I – Circuits

2. People
Benjamin Franklin
Thomas Edison
 Have you heard of these people?
 Why are they important?

3.  Benjamin Franklin
Proved that lightning was electricity by
flying a kite in a lightning storm
Helped people understand the principles
of electricity
• Thomas Edison
– Invented the electrical light bulb

4. What is electricity?
 Electricity is a form of energy
 It is caused by a flow of tiny particles called
electrons through a material

5. Electricity
Electricity is a flow of electric charges along a wire.

6. Electricity
Electricity is a flow of electric charges along a wire.

7. Electricity
Electricity is a flow of electric charges along a wire.

8. Electricity
Electricity is a flow of electric charges along a wire.

9. Electricity
Electricity is a flow of electric charges along a wire.

10. Electricity
Electricity is a flow of electric charges along a wire.

11. Electricity
Electricity is a flow of electric charges along a wire.
This flow of electric charge is called a current.
Current is measured in the units of Amps (A).

12. What is an Electrical
Circuit?
 A circuit is an electrical device that provides a
path for electricity to flow

13. Complete or Incomplete?
 A complete circuit is where all the components of
a circuit are joined up and there are no gaps
 The pathway for electricity is complete

14. Complete or Incomplete?
 An incomplete circuit is where the pathway for
electricity is broken
 The electricity cannot flow

15. Circuit Diagrams
cell switchlamp wires

16. Component Symbols – a
cell
 The cell stores chemical
energy and transfers it to
electrical energy when a
circuit is connected.
 The long line is the positive
end
 The short line is the negative
end

17. Battery
 When two or more cells
are connected together
we call this a Battery.
 The cells chemical energy
is used up pushing a
current round a circuit.
 It is important that each
cell faces the right way

18. Switch
 A switch can be open (as
shown) or closed
 When the switch is open, the
circuit is incomplete – no
electricity can flow
 What happens when the switch is
closed?

19. Bulb / Lamp
 The lamp lights up when
electricity flows through it
 What would happen to a
lamp if there was an open
switch in the circuit?

20. Wires
The wires which carry electricity consist of two parts:
• The metal wires (conductor).
• The plastic coating around the metal wires (insulator).
• Prevents people from being electrocuted.
wires

21. Voltmeter
 The voltmeter measures
the voltage of the circuit
 We will discuss this in
another lesson

22. Ammeter
 The ammeter measures
the current in the circuit
 We will discuss this in
another lesson

23. Resistor
 A resistor can change the amount of current in a circuit
 In a variable resistor, the resistance can be changed.

25. Resistance

26. Variable resistors
Look at Figure 17.6 on page 207.
Path of current flow
Terminal A  metal bar  sliding contact  coils of wire  Terminal B

27. Variable resistors
Look at Figure 17.6 on page 207.
The sliding contact can be adjusted so that the current passes
through only a few coils of wire or many coils of wire.
If the sliding contact is near Terminal A : current passes through
many coils of wire = high resistance
If the sliding contact is near Terminal B: current passes through a
few coils of wire = low resistance

28. Variable resistors
Turn the dial here for
low resistance higher resistance

29. Fuse
 A fuse is a safety device
 When the current is too
high, the fuse breaks
Example
The wire inside a 3A fuse will melt when the current is greater than 3A.

30. Motor
 A motor can be fitted
into a circuit
 What do you think
happens to a motor in
a complete circuit?

31. Circuit Symbols
Voltmeter
Ammeter
Variable Resistor
Switch
Bulb
Motor
Cell
Battery

33. types of circuit
There are two types of electrical circuits;
SERIES CIRCUITS PARALLEL CIRCUITS

34. The components are connected end-to-end, one
after the other.
They make a simple loop for the current to flow
round.
SERIES CIRCUITS
If one bulb ‘blows’ it breaks the whole circuit and
all the bulbs go out.

35. PARALLEL CIRCUITS
The current has a choice of routes (paths).
The components are connected side by side.
If one bulb ‘blows’ there would still be a complete circuit
to the other bulb so it stays lit.

36. measuring current
Electric current is measured in amps (A) using
an ammeter connected in series in the circuit.
A

37. measuring current
A A
This is how we draw an ammeter in a circuit.
SERIES CIRCUIT PARALLEL CIRCUIT

38. measuring current
SERIES CIRCUIT
PARALLEL CIRCUIT
• current is the same
at all points in the
circuit.
6A 6A
6A
• current is shared
between the
components
4A4A
3A
1A

39. copy the following circuits and fill in the
missing ammeter readings.
?
?
4A
4A
4A
3A?
?
1A
?
3A
1A
1A

40. measuring voltage
The ‘electrical push’ which the cell gives to the current
is called the voltage. It is measured in volts (V) on a
voltmeter
V

41. Different cells produce different voltages.
The bigger the voltage supplied by the cell, the bigger
the current (the cell gives a bigger push to the
electrons).
measuring voltage

42. measuring voltage
Unlike an ammeter a voltmeter is connected across
the components (in parallel)
Scientist usually use the term Potential Difference
(pd) when they talk about voltage.

43. Final GPE
Initial GPE
Potential
Difference

44. pd

46. measuring voltage
V
This is how we draw a voltmeter in a circuit.
SERIES CIRCUIT PARALLEL CIRCUIT
V

47. V
measuring voltage
V
V
V

48. series circuit
1.5V
• voltage is shared between the components
1.5V
3V

49. • voltage is the same in all parts of the circuit.
3V
parallel circuit
3V
3V

50. measuring current & voltage
V V
6V
4A
A
A
a)

51. measuring current & voltage
V
V
6V
4A A
A
A
b)

52. answers
3V 3V
6V
4A 4A
6V
6V
6V
4A 4A
2A
2A
4A
a) b)