grade 8 electricity

2. •A form of energy
from movement
of electrons.
•Comes from the
Greek word
“electron”
ELECTRICITY

3. ELECTRICITY
•It is associated with
electric charge, a
property of
subatomic particles.
•Charges can be
stationary or
moving.

4. Unlike
charges
ATTRACT
like
charges
REPEL

5. STATIC ELECTRICITY
•The temporary
building up of charge
on an object
•Some atoms hold
electrons more
tightly than others.

6. STATIC ELECTRICITY
•Charging by
conduction happens
when a charged
object touches
another object and
electrons are
transferred

7. STATIC ELECTRICITY
• Charging by induction happens when a
charged object and is held close to
another object and that causes charges
to be rearranged

8. STATIC ELECTRICITY
•Charging by
friction happens
when objects rub
together and
electrons are
transferred.

9. Insulators and Conductors
• Some materials allow charges to be
transferred (conductor) while others do
not (insulator)

10. Insulators and Conductors
• Conductors:Gold,Silver,Copper,Iron,Lead
,Salt and Water.
• Insulators: Plastics,Glass,Dry air, and
Wood

11. Electric Current
•Flow of charges
•The electric
charge in a
current is carried
by minute
particles called
electrons.

12. Electric Current
•For electricity
to flow, you
need a closed
continuous
path, called
circuit

13. Current
• The measure of
how many
electrons per
second.
• Also called
amperage
• Measured in
amperes

14. Current
•AC is an electric current that
regularly reverses direction
Alternating Current (AC)

15. • DC is an electric current that flows in
only one direction and has a fairly
constant average value
Direct Current (DC)
Current

19. • In addition, for electrons to flow there
must be a potential difference between
two places
Remember: Electric potential energy-
two unlike charges
Lower potential
energy
Higher
potential
energy

20. Lower
potential
High
potential
electrons
Direction of flow
• Electrical pressure
• Charges flow from high voltage
to low voltage or from high PE
to low PE
Voltage

24. • Cells can cause voltage
that makes electrons
flow
• There are two kinds
electrochemical cells,
wet cells such as
battery and cells like
flashlight
Electrochemical Cell

25. • When two or more cells are
connected together we call this a
battery
Electrochemical Cell

26. • The cells chemical energy is used
up pushing a current round a
circuit. Current is Direct Current
Electrochemical Cell

27. • Allesandro Volta (1800) cell
Electrochemical Cell

28. • Wet Cell = Car Battery
Electrochemical Cell

29. • Dry Cell = Household “Battery”
Electrochemical Cell

30. • What occurs in a wire when the
circuit switch is closed?
Electrochemical Cell

31. • The tendency for a
material to oppose the
flow of electrons
• Different materials have
different amounts of
resistance to the flow of
electrons.
• The unit of resistance is
ohm (Ω)
Resistance

32. • Resistance in wires
produces a loss of
energy
(usually in the form of
heat), so materials
with no resistance
produce no energy loss
when current pass
Resistance

33. • Thin wires provide more resistance than do
thick wires
Which materials has higher
resistance?

34. • Insulators have high resistance
Which materials has higher
resistance?

35. • Resistance also
depends on
temperature, usually
increasing as the
temperature
increases resistance
Which materials has higher
resistance?

36. • To make the circuit, these components are
connected together with metal connecting
wires
CIRCUITS
switch
Cell wires
lamp

37. • To make the circuit, these components are
connected together with metal connecting
wires
CIRCUITS
switch
Cell wires
lamp
• When the switch is turned on (open), the lamp
lights up. This is because there is a continuous
path of metal for the electric current to flow
around.

38. CIRCUITS
• Scientist usually draw electric circuits
using symbols.
Cell lamp Switch Wires

39. CIRCUITS

40. TYPES OF CIRCUIT
SERIES PARALLEL