Break circuits F uses are used to break circuits if the current passing through it is TOO LARGE that may probably cause damages to the appliances.

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