Fuses are used to break circuitsbreak circuits if the current passing

through it is TOO LARGE that may probably cause damages to the appliances.

Typical fuse ratings :0.1 A, 0.5 A, 1 A, 3 A, 5A, 13 A, 15 A, 30A, etc.

* If the current in the circuit is greater than the fuse rating, the fuse breaks the circuit then.

* Heater (220V, 2200 W)Operating current or max. current = P / V = 2200 / 220= 10 A

Which fuse rating should be chosen in order to protect the heater?A. 5A B. 10A C. 13A D. 15A

* e.g. Operating current (max. current) Fuse rating chosen0.25 A0.5 A2.5 A3 A3.5A 5A

1A1A3A5A

Circuit Breaker

Electricity Meter / Kilowatt-hour meter (kWh meter)

1 kWh =

* kWh : unit of electricity

* 1 kWh = 1 unit

= (1000 W) (60 x 60 s)

= 3600 000 J

(1 kW) (1 hr)

UnitsUnits consumedconsumed

Amountcharged forelectricity

The HongKongElectric Co. Ltd香港電燈有限公司

Name & AddressName & Address

China Light and PowerHong Kong Ltd中華電力有限公司

Total units consumed= 713

For first 400 units,$0.862 per unit.

Others : $0.932 per unit

Total amountcharged for electricity= $ 344.80 + $291.72= $ 636.52

Average cost of electricity= $ 636.52 / 713= $ 0.893

Other charges