Electrical EngineeringCHAPTER 14

Electrical Engineering (404)

Electricity is all around us. It runs our homes, offices and schools.

Designing and developing electrical systems is what electrical engineers do.

All electrical appliances (like toasters) & electronic devices depend on electrical circuits.

Electrical components (diodes and transistors) are called semiconductors and are made of silicon.

Electrical Circuits (404)

The conventional current flow is from the positive terminal to the negative terminal.

Types of Current (404) AC Alternating current charges

continuously change direction forward and back at 60 Hz

Example: outlets (approx 120 V)

DC Direct current charges move in one direction

Example: batteries

Power Supply (404)

For a electrical or electronic circuit to work, it needs a power supply.

Read p.463 for examples of power supplies.

Conduction (404)

The wires in our circuits must be made of a conductive material. Usually copper.

Other things besides wires can conduct. The human body can conduct electricity.

Printed Circuits (466)are an electrical circuit printed on a solid support. They can also be called circuit boards.

Insulators (404)

a. Insulators are poor conductors.

b. They prevent electricity from leaving the wire.

c. Example: rubber and plastic

Protection (404)

Our homes are equipped with fuses and circuit breakers which are there to prevent serious accidents.

Example: When too many appliances are plugged into an outlet, the electricity goes out.

Resistance (466)

It limits the flow of electrons.

It is usually indicated with a colour code.

See handout.

2

unit ohm,

V Js1 1 1

A C

Resistance (466)

Depends on: Length, cross sectional area, material, and temperature.

Resistance and Temperature

Resistance and Thickness

Capacitor (466) p.473

A capacitor is a storehouse of charge and energy that can be reclaimed when needed for a specific application.

A capacitor is made up of two metal plates close to each other and separated by an insulating material called a dielectric.

Capacitance (466) p.473-474

Capacitance: The ability of a conductor to store energy in the form of electrically separated charges

Capacitance is the ratio of charge to potential difference

unit Farad, F

C1F=1

V

Diodes (466) p.474

A diode is a small device when put in an electric circuit allows current to flow in one direction but not the other.

Example: LED (Light Emitting Diodes)