Practical Electricity

Neutral wire

-Blue -completes circuit by forming path for current back to supply

Live wire

-Brown -Delivers current at high voltage from supply to applaience

Switches

-Fitted into live wire,so that switching off disconnects the high voltage from the appliance, if connected to neutral,aplliance could be live -Connect and disconnect the circuit -

Earth wire

-Green and yellow -low resistance, connected to metal casing

Heating in Electric Iron

-Heat is generated when current passes through the heating element -Heat is spread out thanks to the large surface area of the metal iron,which is a good conductor of heat -A thermostat inside the iron controls the temperature of the heating element.

Heating in Electric Kettle

-Heating element is encased in a metal tube -Heat is generated when current passes through heating element -Water surrounding the heating element gets heated and heat is transferred throughout the water by conduction and convection

Nichrome wire is used as heating element in electric iron and kettles

-Nichrome has high melting point -High density -does not oxidise easily

Earthing

-Protects user from electric shock if metal casing becomes live -The large current flows to the ground through the earth wire,as it has a much lower resistance than the person -Person no electric shock

Circuit breakers

-Safety devices that switch off the electrical supply when there is a overflow of current

Double insulation

-Substitute for earth wire -In addition to first insulation on wire, there is 2nd insulation

Fuse

-safety device that protect the equipments against excessive current flow -Fuse wire made up of tin-lead alloy that has a low melting point,when current becomes to large,fuse heats up and melt, cutting of the circuit -Fuse rating 1A,3A,5A,10A,13A -Fuse used should be slightly above current -Fuse connected to live wire,so that appliance wont become live after fuse blown

Electrical Hazards

Damaged insulation -live wire come in contact with metal casing Overheating of cables -insulation to melt,starting fires Damp conditions -electric shock

Formulas in practical electricity

E=VQ E is electrical energy (Joules) P=IV P is power (Watts)

Cost of electrical appliances

Measured in KWh *Make sure units are KW and hr

Wiring plug

Neutral Earth Live