ELECTRICAL ENGINEERINGTechnological World

Electrical FunctionAn electrical function is the role that a

component plays in the control or transformation of electric current.

Power SupplyPower supply is the electrical function

performed by any component that can generate or provide an electric current in a circuit.BatteryElectrical OutletPhotovoltaic Cell

BatteriesBatteries transform the energy from a

chemical reaction into electrical energy.Advantages:

PortabilityDisadvantages:

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 OutletWhen 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 supplyHydro-electricity creates very little greenhouse gas

Disadvantages:Appliances cannot be moved far from the wall outletAppliances stop working in the event of a power

shortageApplications: TVs, Fridges, Computers

Photovoltaic CellPhotovoltaic (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 devicesDo not cause greenhouse gas emissions

Disadvantages:Their operation depends on sunny conditions.Very expensive

Applications: Solar homes, solar cars, calculators

ConductionConduction 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 CircuitsA 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.

InsulationInsulation 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.

ProtectionProtection 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.

FusesThe 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.

BreakersIn 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.

ResistanceA 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.

ResistanceElectrical resistance is expressed in ohms –

represented by the Greek letter omega [Ω]

Ex: Resistor ‘A’ has an electrical resistance of 2500Ω.

ResistanceResistance 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.

DIGIT 0 1 2 3 4 5 6 7 8 9 Gold SilverMULTIPLIER 1 101 102 103 104 105 106 107 108 109

TOLERANCE ± 20% ± 5% ± 10%COLOR BLACK BROWN RED ORANGE YELLOW GREEN BLUE VIOLET GREY WHITE GOLD SILVER

THE COLOR CODE FOR ELECTRICAL RESISTORS:

Resistance