Summary Technology Grade 9 IEB Electrical Technology Notes

Electrical Technology
Application based, don’t learn word for word
 Impact of electricity (flow of energy) – we can’t live without it!
 Comes from natural resources: Coal, hydropower, sun
 Power station (starting place)- where electricity comes from

The Differences between an Electrical and
Electronic System
 Electrical Systems
 Often supply electricity to a machine
 Have no level of intelligence
 Usually work on higher voltage levels
 Have one input and one output
 An electrical drill is an example of an Electrical System
 Electronic Systems
 Have a level of intelligence e.g. switching on a device etc.
 Work on smaller voltage levels
 Have multiple inputs and outputs
 A cell phone is an example of an Electronic System

ELECTRONIC – Multiple inputs and outputs (Many uses & purposes)
POWER ELECTRONIC – e.g. microwave (can do a purpose along with other things)
ELECTRICAL- 1 Input, 1 Output

 Alternating Current – the type of electricity that comes from a plug
(AC) Changes polarity


 Direct Current – comes from a battery (Portable)
(DC) Does not change polarity


 Oscilloscope – An instrument to measure the current


Atomic Theory
 Electricity – the movement of a valence electron from one atom to another
 Protons (+) positively charged
 Neutrons are uncharged
 Electrons are -ive (negatively) charged
 Building blocks of Matter – occupies space & has mass
 Atomic theory is the scientific theory of the nature of matter.
 Matter is made up of small particles called atoms.
 Atoms consist of even smaller particles called electrons, protons and neutrons.

,  Nucleus - protons and neutrons form the central part of this.
 When two, three or more atoms form chemical bonds with each other, they form
molecules.
 Atoms can be the same or different from each other in one molecule
 Like (the same ) charges repel each other and unlike (different) charges attract each
other.
 In an electric circuit the electrons (negative charges) will flow away from the negative
terminal of the battery or other power supply and they move towards the positive
terminal.
 Called the Electron flow direction
 Any free positive charge (e.g. positive ions, cat-ions, holes and protons) were to move
in a circuit - they would move away from the positive terminal of the battery towards the
negative terminal of the battery.
 Called conventional flow direction of current.
 Current flow (l) is the rate of flow of charge (Q).
 Charge is measured in units called Coulombs and current is measured in Amperes
(Amps)
l= Q
t Q=l x t

Nucleus
 Consists of positively charged protons and uncharged neutrons.
 More or less the same size and weight.
 Nuclear glue” that holds the nucleus together and is called nuclear forces
 There may also be a sub-nuclear particle called a gluon that holds the nuclear together.

Electrons
 To keep an atom electrically stable, it must have an equal number of electrons
(negative) in orbit around the nucleus of protons (positive) in the nucleus.
 Atom called an ion - when there are either more or less electrons in orbit compared to
protons in the nucleus.
 Happens in static electricity and in some chemical solutions.

Electron Shells
 When electrons are arranged in shells or orbits around the nucleus.
 Electrons have different amounts of energy.

Valence shell
 The outer most shell of any atom

Valence electrons
 These are the electrons in the outer most shell or energy level of an atom.
 These are the electrons that take part in forming chemical bonds.