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Module 3 Electrical Fundamentals

ATTEMPT THE QUESTION SET AGAINST EACH SUB-MODULE FOR REALTIME ASSESMENT AND FEEDBACK WITH SCORING

Sub-Module 01-Electron Theory

Structure and distribution of electrical charges within: atoms, molecules, ions, compounds;Molecular structure of conductors, semiconductors and insulators.

Sub-Module 02-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.

Sub-Module 03-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.

Sub-Module 04-Generation of Electricity

Production of electricity by the following methods: light, heat, friction, pressure, chemical action, magnetism and motion.

Sub-Module 05-DC Sources of Electricity

Construction and basic chemical action of: primary cells,secondary cells,lead acid cells,nickel 2 2 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.

Sub-Module 06-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.

Sub-Module 07-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.

Sub-Module 08 - Power

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

Sub-Module 09 - 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.

Sub-Module 10 -Magnetism

(a) Theory of magnetism; Properties of a magnet; Action of a magnet suspended in the Earth's magnetic field; Magnetization and demagnetization ; 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.

Sub-Module 11-lnductance/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.

Sub-Module 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.

Sub-Module 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.

Sub-Module 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; 2 2 Power dissipation in L, C and R circuits; Impedance, phase angle, power factor and current calculations ;True power, apparent power and reactive power calculations.

Sub-Module 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 offline and phase voltages and currents, calculation of power in a three phase system; Primary and Secondary current, voltage, turns ratio, power, efficiency; Auto transformers.

Sub-Module 16 - Filters

Operation, application and uses of the following filters: low pass, high pass, band pass, band stop.

Sub-Module 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.

Sub-Module 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.

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