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Electronic Power Supply


The electric current supplied to your home from the power station is alternating current, or AC for short. AC reverses its direction of flow 100 times every second. It flow 50 times in one direction, say to the power station; and 50 times in the other direction, say from the power station. AC is easier to generate and to transmit than DC (Direct Current). Another reason that AC is used for domestic power supplies is that its voltage can be changed bu a device called a transformer.

High quantities of electrical energy are produced by a power station. All this electricity must be sent out across the country to houses, shops, and factories. To push the electricity out over long distances, very high voltages are needed. However, when the electricity reaches its destination, lower voltages are needed because high voltages are very dangerous.

High voltages are ‘steep-down’ by means of a transformer, an invention of the nineteenth-century English scientist Michael Faraday, who also discovered the principle of dynamo. The dynamo can change mechanical energy into electrical energy. The transformer consists of two coils of wire (both wound on the same iron core), one coil having more turns of wire than the other. If AC is passed through the coil, it induces moving lines of magnetic force. This is turn induces an electric current in the other coil. Suppose coil A has half as many turns as coil B, then the voltage induced in it will be half the voltage in coil B. In this way the voltage can be reduced. At the same time the current can be increased.

The power  supply from the power station is stepped-down by transformers from hundreds of thousands of volts to 220 volts for domestic use. Houses are wired with electric circuits. Electricity coming into the house passes through a meter, which measures the amount of electricity used, so that the supplier can charge for it. The current also passes through  fuse box. A fuse protects electrical appliances from over loading. If too much power is taken, a wire in the fuse gets hot and melts, so breaking the circuit and acting as a ‘switch’.

  • alternating current – arus bolak balik
  • reverse – membalikkan
  • say – misalnya
  • generate – membangkitkan
  • domestic power supply – penyediaan tenaga di rumah
  • device – alat
  • power station – pusat pembangkit tenaga listrik
  • coil of wire – lilitan kawat, kumparan
  • induce – menimbulkan
  • be wired – dilengkapi dengan instalasi kawat listrik
  • electric circuit – lingkaran listrik
  • meter – alat pengukur
  • charge – memungut biaya

  • electrical appliances – alat-alat rumah tangga yang djalankan dengan listrik
  • electric waterpump – pompa air listrik
  • washing machine – mesin cuci
  • electric iron – setrika listrik
  • electric fan – kipas angin listrik
  • electric razor – alat cukur listrik
  • refrigerator – lemari es
  • air-conditioner – alat pendingin (AC)
  • vacuum cleaner
  • electric bulb – lampu TL (neon)
  • electric motor – elektromotor
  • electric meter – meteran listrik
  • plug – steker
  • plug in – memsukan steker
  • extension cord – kabel penyambung
  • switch – saklar, tombol
  • switch on/off – menyalakan/memadamkan
  • the radio is on – radionya hidup
  • the fuse has blown – sekringnya putus
  • fuse box – kotak tempat sekring
  • short circuit – korslet

An electric motor consists of a coil of wire and a magnet. When an electric current flows in the coil it become magnetized. The magnetic poles of the coil are attracted by the opposite of the magnet dan are repelled by the like poles. This cause a turning movement. Current is fed to the coil via the brushes and commutator. The commutator reverses the flow of current in the coil every half rotation, so that the coil’s poles continually change places. In this way the coil is made to rotate continuously in the same direction.

  • coil of wire – lilitan kawat
  • current – aliran, arus
  • repel – menolak
  • like – yang sama
  • be fed – dimasukkan
  • commutator – pembalik arah
  • reverse – membalikan
  • change-places – bertukar tempat

 

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