ELECTRONICS
ELECTRONICS: This is the branch of physics that deals with the emission and effects of electrons in
materials.
❖ Electronic systems or circuits are made up of various components connected to each other.
USES OF ELECTRONIC CIRCUIT
The main uses of electronic circuit are:-
❖ Conversion and distribution of data.
❖ Controlling and processing of data.
❖ Electronic components can be:-
i) Passive
ii) Active
i) PASSIVE COMPONENTS
❖ Passive components consume but do not produce energy.
❖ They do not have the ability to produce gain (increase the power or amplitude of a signal).
❖ They do not have also direction (they operate in the same way regardless of the direction of
current flowing through them.
❖ Passive components include power sources (battery or generator), resistors, capacitors and
inductors.
INDUCTOR: - Is a coil which induces e.m.f through itself.
ii) ACTIVE COMPONENTS
• Are those that have direction and the capacity to produce gain.
❖ They include semiconductor devices such as diodes, transistors, and integrated circuits.
ENERGY BANDS
❖ These are energy values through which conductor occur.
❖ These are the series of “allowed” and “forbidden” energy bands that is contains.
❖ Energy band determines a material’s electronic properties.
BAND THEORY: Is the theory which is based on the fact that in crystals, electrons fall into allowed
energy band.
TYPES OF BANDS
i) Valence band
ii) Forbidden band/ band gap
iii) Conduction band
i) VALENCE BAND
• This is the one which contains free electrons which can jump to other band when they tend to
absorb sufficient amount of energy.
The valence band is situated closer to the nucleus of an atom.
ii) FORBIDDEN BAND/BAND GAP
• This is the one which is situated between the valence and conduction bands
❖ It contains no charge carrier at all (it is an empty band).
iii) CONDUCTION BAND
• This is the one which contains very few electrons and it is sometimes contains no electrons.
❖ The free electrons in valence band may jump to the conduction band when they absorb energy.
❖ Thus; the conduction process takes place in the conduction band.
THE FERMI LEVEL
• This is a solid at which the half of the quantum states is occupied.
❖ At absolute zero (0K) Kelvin, electrons will be in the lowest energy levels.
❖ The uppermost of these levels is called the Fermi level.
ELECTRICAL MATERIALS
• These are materials used in electrical circuits.
CLASSIFICATIONS OF ELECTRICAL MATERIALS
1. Insulators/Non-conductors
2. Conductors
3. Semi-conductors
1. INSULATORS/ NON-CONDUCTORS
• These are materials that do not allow electricity to pass through.
❖ In this materials the forbidden gap is very wide, thus no electrons are able to cross the forbidden
gap.
PROPERTIES OF INSULATORS
In insulators:-
▪ Valence band is full of electrons
▪ Conduction band have no electrons
▪ Cannot conduct electricity
▪ Forbidden gap is higher, hence an electrons to jump from valence to conduction band, very large amount of energy must be applied which is difficult to get the energy required.
❖ Examples of insulators are glass, mica, paraffin, hard rubbers and plastics.
EFFECT OF TEMPERATURE IN INSULATORS
❖ The temperature has no effect on the conductivity property of the insulator since the forbidden
gap is very large.
2. CONDUCTORS
• These are materials that allow electricity to pass through.
❖ Conductors have negligible forbidden gap, that is valence and conduction bands overlap.
❖ The electrons migrate easily from valence to conduction band.
