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
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
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.
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
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?
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.
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
4A
4A
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.
