Download SCIENCE 10 – Power Supply Conduction Insulation

Technological World
Electrical Function
 An electrical function is the role that a component
plays in the control or transformation of electric
current.
Power Supply
 Power supply is the electrical function performed by
any component that can generate or provide an electric
current in a circuit.
 Battery
 Electrical Outlet
 Photovoltaic Cell
Batteries
 Batteries transform the energy from a chemical
reaction into electrical energy.
 Advantages:
 Portability
 Disadvantages:
 Must be replaced after a certain amount of time
 Can contaminate the environment if not disposed of
properly
 Applications: mp3 players, watches, remote controls
Electrical Outlet
 When the prongs of an electric plug enters an outlet,
contact is made with parts permanently connected to
an electrical network.
 Advantages:
 Stable & long-lasting power supply
 Hydro-electricity creates very little greenhouse gas
 Disadvantages:
 Appliances cannot be moved far from the wall outlet
 Appliances stop working in the event of a power
shortage
 Applications: TVs, Fridges, Computers
Photovoltaic Cell
 Photovoltaic (solar) cells generate an electric current
when exposed to light.
 Advantages:
 Can power equipment in isolated areas without access to
power grids.
 Can also power portable or mobile devices
 Do not cause greenhouse gas emissions
 Disadvantages:
 Their operation depends on sunny conditions.
 Very expensive
 Applications: Solar homes, solar cars, calculators
Conduction
 Conduction is the electrical function performed by
any component that can transmit electric current from
one part of a circuit to another.
 Electricity is primarily conducted through wiring –
usually copper.
 Components other than wires can also act as
conductors.


Ex: two pieces of metal that come into contact
Ex: the human body
Printed Circuits
 A printed circuit is an electrical circuit printed on a
solid support called a circuit board.
 Printed circuits have replaced copper wires for the
purposes of conduction in smaller electronic devices
such as cell phones and MP3 players.
 A printed circuit is usually a plastic board 1mm thick
covered in a thin layer of copper. The circuit board is
then etched and finally all the excess copper is
removed leaving only the electrical circuit printed on
the board.
Insulation
 Insulation is the electrical function performed by any
component that prevents an electric current from
flowing.
 Insulators are poor conductors so they prevent
electrons from leaving wires.
 Plastics & ceramics make for good insulators.
Protection
 Protection is the electrical function performed by any
component that can automatically cut current flow in
the event of a power surge.
 If a short circuit or electrical overload occurs, in order
to avoid serious accidents like fires or shocks and to
avoid damaging plugged in appliances, protective
devices such as fuses or breakers can be connected to
the electrical circuits.
Fuses
 The electric current crosses the fuse through a
conductive filament.
 If the current intensity exceeds a certain level, the
filament melts and breaks, preventing the current
from flowing through the fuse.
 The fuse then needs to be replaced.
Breakers
 In some breakers, the current passes through a
bimetallic strip. Other breakers use an
electromagnetic mechanism.
 When the current intensity exceeds a certain level, the
strip becomes hot, it bends, and the connection is
interrupted.
 In order to restore circuit operation, the breaker switch
must be switched back. The breaker does NOT need to
be replaced.
Resistance
 A resistor is a component designed to limit the flow
of electrons through an electrical circuit.
 A resistor acts like a small-diameter pipe in a water
supply system. Even if a large volume of water is
present, the water flow will be restricted by the size of
the small pipe. Resistors function in a similar way, by
hindering the flow of electrons through a circuit.
Resistance
 Electrical resistance is expressed in ohms –
represented by the Greek letter omega [Ω]
 Ex: Resistor ‘A’ has an electrical resistance of 2500Ω.
Resistance
 Resistance is usually indicated with a color code.
 The color of the first band corresponds to the first digit.
 The color of the second band corresponds to the second
digit.
 The color of the third band corresponds to the multiplier.
 The color of the fourth band corresponds to the tolerance.
THE COLOR CODE FOR ELECTRICAL RESISTORS:
DIGIT
MULTIPLIER
TOLERANCE
COLOR
0
1
± 20%
BLACK
1
101
2
102
3
103
4
104
5
105
6
106
7
107
8
108
9
109
Gold
± 5%
BROWN
RED
ORANGE
YELLOW
GREEN
BLUE
VIOLET
GREY
WHITE
GOLD
Silver
± 10%
SILVER
Resistance