ELECTRICITYELECTRICITY

PhysicsPhysics

EDD 5161F (Gp 4)EDD 5161F (Gp 4)Lee Wing Ying (97096920)Lee Wing Ying (97096920)

Chan Pui Ching (97038100)Chan Pui Ching (97038100)Wong Lai Yuk (97029290)Wong Lai Yuk (97029290)

Target audience: F.3

Basic knowledge:

Unit of electricity

Simple Calculation about Electricity

ContentContent

Electrical PowerElectrical PowerUnit of electricityUnit of electricityKilowatt-hour meterKilowatt-hour meterMain CircuitMain Circuit

Electrical PowerElectrical Power

Power = Energy change / timeunit of power: Watt (W)unit of energy: Joule (J) unit of time: second (s)1W = 1Js-1

Unit of ElectricityUnit of Electricity

- - The energy consumed in household appliances The energy consumed in household appliances is measured in is measured in kilowatt-hours (kWh)kilowatt-hours (kWh)

- - One kilowatt-hour is the amount of energy One kilowatt-hour is the amount of energy that is used by a 1000 W appliance in one hour. that is used by a 1000 W appliance in one hour.

Appliance Rating/W Operating Energy used Cost per time per day per day day/$

Clock 5 24TV 40 7Karaoke 200 2Heater 1500 8Total per day Total in June

The total cost of electricity consumption in June

0.120.280.412

0.0840.1960.288.4

12.8384

8.96268.8

Electricity BillElectricity Bill

Chan Tai Man13 Nathan RoadKowloon

85467-253-07

Chan Tai Man13 Nathan RoadKowloon

28-04-98共 日用電量

由 至59

01-03-98 28-04-98

06-05-98

Kilowatt-hour meterWhen the mains cable enters the home, it is connected through a fuse to a kilowatt-hour meter.

Main CircuitMain CircuitLive wire (Live wire ( 火線火線 ))This carries the alternating current to the applianceThis carries the alternating current to the appliance.

Neutral wire (Neutral wire ( 中線中線 ))This carries the alternating current to the applianceThis carries the alternating current to the appliance.

It connects the metal body of the appliance to the earth.It connects the metal body of the appliance to the earth.If a live wire becomes loose and touches the metal body,If a live wire becomes loose and touches the metal body,a large current flows to earth. The person does not get ana large current flows to earth. The person does not get anelectric shock.electric shock.

Earth wire (Earth wire ( 地線地線 ))

Standard Socket and PlugStandard Socket and Plug

WireWire SymbolSymbol ColourColourLive L brownNeutral N blueEarthEarth EE green and yellowgreen and yellow

Wiring in a 3-pin plugWiring in a 3-pin plug

The live wire is joined to the live pin through a cartridge fuse. The other wires are screwed directly to their corresponding pins.

E

N

L

Appliances with an earth and a fuseAppliances with an earth and a fuse

FUSE YX

Z

X is Y isZ is

NeutralLiveEarth

Through a faulty kettle with earthing

BOMBBOMBBOMB

Through a faulty kettle without fusing and earthing

The ring circuitThe ring circuitEarth

Live

Neutral

Circuit in our home

Neutral Live

Neutral Live

Example:

Neutral Live

Example:

http://www.hec.com.hk

Hong Kong Electric Holdings Ltd.

China Light & Power Co. Ltd.

http://www.chinalightandpower.com.hk

Two Electrical Suppliers in Hong Kong:

THE ENDTHE END