Module 3

MODULE 3. ELECTRICAL FUNDAMENTALS
3.1 Electron Theory
    Structure and distribution of electrical charges within: atoms, molecules,

    ions, compounds; Molecular structure of conductors, semiconductors and insulators.

3.2 Static Electricity and Conduction
    Static electricity and distribution of electrostatic charges;
    Electrostatic laws of attraction and repulsion;

    Units of charge, Coulomb's Law;
    Conduction of electricity in solids, liquids, gases and a vacuum.

3.3 Electrical Terminology
    The following terms, their units and factors affecting them: potential
    difference, electromotive force, voltage, current, resistance, conductance,
    charge, conventional current flow, electron flow.

3.4 Generation of Electricity

    Production of electricity by the following methods: light, heat, friction,

    pressure, chemical action, magnetism and motion.

3.5 DC Sources of Electricity
    Construction and basic chemical action of: primary cells, secondary cells, 

    lead acid cells, nickel cadmium cells, other alkaline cells;

    Cells connected in series and parallel; Internal resistance and its effect on a battery;
    Construction, materials and operation of thermocouples;
    Operation of photo-cells.

3.6 DC Circuits
    Ohms Law, Kirchoff's Voltage and Current Laws;
    Calculations using the above laws to find resistance, voltage and current;
    Significance of the internal resistance of a supply.

3.7 Resistance/Resistor
    (a) Resistance and affecting factors;
    Specific resistance;
    Resistor colour code, values and tolerances, preferred values, wattage
    ratings;
    Resistors in series and parallel;
    Calculation of total resistance using series, parallel and series parallel combinations;
    Operation and use of potentiometers and rheostats;
    Operation of Wheatstone Bridge.
    (b) Positive and negative temperature coefficient conductance;
    Fixed resistors, stability, tolerance and limitations, methods of construction;
    Variable resistors, thermistors, voltage dependent resistors;
    Construction of potentiometers and rheostats;
    Construction of Wheatstone Bridge;

3.8 Power
    Power, work and energy (kinetic and potential);
    Dissipation of power by a resistor;
    Power formula;
    Calculations involving power, work and energy.

3.9 Capacitance/Capacitor
    Operation and function of a capacitor;
    Factors affecting capacitance area of plates, distance between plates, number of plates, dielectric

    and dielectric constant, working voltage, voltage rating;

    Capacitor types, construction and function;
    Capacitor colour coding;
    Calculations of capacitance and voltage in series and parallel circuits;
    Exponential charge and discharge of a capacitor, time constants;
    Testing of capacitors.

3.10 Magnetism
   (a) Theory of magnetism;
         Properties of a magnet
         Action of a magnet suspended in the Earth's magnetic field;
         Magnetisation and demagnetisation;
         Magnetic shielding;
         Various types of magnetic material;
         Electromagnets construction and principles of operation;
         Hand clasp rules to determine: magnetic field around current carrying conductor.

   (b) Magnetomotive force, field strength, magnetic flux density, permeability,
         hysteresis loop, retentivity, coercive force reluctance, saturation point, eddy currents;
         Precautions for care and storage of magnets.

3.11 Inductance/Inductor
        Faraday's Law; Action of inducing a voltage in a conductor moving in a magnetic field;

        Induction principles;
        Effects of the following on the magnitude of an induced voltage: magnetic field strength, rate of 

         change of flux, number of conductor turns;

        Mutual induction;
        The effect the rate of change of primary current and mutual inductance has on induced voltage;
        Factors affecting mutual inductance: number of turns in coil, physical size of coil, permeability

         of coil, position of coils with respect to each other;

        Lenz's Law and polarity determining rules; Back emf, self induction;

        Saturation point;
        Principle uses of inductors;

3.12 DC Motor/Generator Theory
        Basic motor and generator theory;
        Construction and purpose of components in DC generator;
        Operation of, and factors affecting output and direction of current flow in DC generators;

        Operation of, and factors affecting output power, torque, speed and direction of rotation of DC

          motors;

        Series wound, shunt wound and compound motors; Starter Generator construction.

3.13 AC Theory
       Sinusoidal waveform: phase, period, frequency, cycle;
       Instantaneous, average, root mean square, peak, peak to peak current values and calculations of 

        these values, in relation to voltage, current and power Triangular/Square waves;

        Single/3 phase principles.

3.14 Resistive (R), Capacitive (C) and Inductive (L) Circuits
       Phase relationship of voltage and current in L, C and R circuits, parallel, series and series

        parallel;

      Power dissipation in L, C and R circuits;
      Impedance, phase angle, power factor and current calculations; True power, apparent power and

       reactive power calculations.

3.15 Transformers
        Transformer construction principles and operation; Transformer losses and methods for 

          overcoming them;

       Transformer action under load and no-load conditions; Power transfer, efficiency, polarity 

         markings;

       Calculation of line and phase voltages and currents;
       Calculation of power in a three phase system;
       Primary and Secondary current, voltage, turns ratio, power, efficiency;
       Auto transformers.

3.16 Filters
       Operation, application and uses of the following filters: low pass, high pass, band pass, band 

         stop.

3.17 AC Generators
        Rotation of loop in a magnetic field and waveform produced;
        Operation and construction of revolving armature and revolving field type AC generators;
        Single phase, two phase and three phase alternators;
         Three phase star and delta connections advantages and uses;
         Permanent Magnet Generators.

3.18 AC Motors
        Construction, principles of operation and characteristics of: AC synchronous and induction                    motors both single and polyphase;
        Methods of speed control and direction of rotation;
         Methods of producing a rotating field: capacitor, inductor, shaded or split pole.