[8] GENERATION OF ELECTRIC

8.1 Generation of Electrical Energy- types of electric generator: i) hydroelectric generatorii) thermal generatoriii)diesel generatoriv)gas turbine generatorv)nuclear generator

hydroelectric generator

Fuel : NoEnergy changes:Potential energy kinetic energy electrical energy

thermal generator

Fuel: Coal / petroleumEnergy changes:Chemical E. heat E. potential E. kinetic energy electrical energy

diesel generator

Fuel: DieselEnergy changes:Chemical E. heat E. potential E. kinetic energy electrical energy

gas turbine generator

Fuel: Natural gasEnergy changes:Chemical E. heat E. potential E. kinetic energy electrical energy

nuclear generator

Nuclearreactorreactor

Fuel: plutonium / uraniumEnergy changes:Chemical energy nuclear energy heat E. potential E. kinetic energy electrical energy

8.2 TRANSFORMERFunction change the voltage of alternating current (a.c.)

Type of transformer:Step-up transformer

Step-down transformer

Symbol

Increase the voltage of alternating current (a.c.)FunctionDecrease the voltage of alternating current (a.c.)

No. of turns in secondary coil ismore thanthe no. of turns in primary coilNo. of turns in secondary coilVsNo. of turns in primary coilNo. of turns in secondary coil isless thanThe no. of turns in primary coil

Output voltage is more than input voltageOutput voltage vs input voltageOutput voltage is less than input voltage

Relationship between no. of turns in secondary coil, no. of turns in primary coil, output voltage and input voltage:

Input voltagenumber of turns in primary coil=output voltagenumber of turns in secondary coil

8.3 Electricity Transmission and Distribution System

National Grid Network (NGN)- link all power station in the country - advantages: Ensure continuous supply of electrical energy. Electrical energy can be channeled to other generator depend to the need.8.4 Electricity Supply and Wiring system at Home

Electrical energy that supply to home is alternating current(a.c.) at 240V. Supplier unit consist of main fuse and electric meter. Consumer unit consist of main switch, miniature circuit breaker (MCB) and earth leakage circuit breaker (ELCB). Earth wire was connected to the body/casing of electrical appliances

ComponentFunction

3-pin plug

Type of wireColour

Single phase and triple phase wiring system

Figure 8.13, pg 161(text book)

8.5 Cost of Using Electrical Energy S.I. unit for power is watt(W) and other unit is joule per second (J/s). In malaysia, electrical energy is mesured in unit of kilo-watt-hour(kWh) Power is rate of energy used (energy used per second).

JPTPVI

8.6 Function of Fuse and Earth Wire

Fuse: Function prevent excess current from flowing through electrical appliances. Type of fuse: Glass cartridge fuse Wire fuse Fuse value 2A, 3A, 5A, 10A, 13A, 15A Identify suitable fuse by using formula:

The fuse value must be slightly higher than the current.

Earth Wire Connect the casing of electrical appliance to the earth. Channel leakage current into earth (earthing)

8.7 Safety Precautions in Used of Electrical Energy

Causes of Electric Accidents:i) Short circuit.ii) Overheated insulation.iii) Overloading outlet iv) Damage old wirev) Replace burn fuse with wirevi) Handling electrical applience with wet handvii) Repairing electrical faults

Safety Features in Electric Circuit:i) Insulation wireii) International colour codeiii) Switchesiv) Fusesv) Earthingvi) Automatic circuit breaker (MCB, ELCB)

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