2. Supply (n): a source of electrical energy In Turkey, electrical supply is provided by some organisations such as EnerjiSA, Başkent Elektrik etc. Current(n): the flow of electricity through a wire, etc A 15 amp electrical current

3. alternate (v): to happen or exist one after the other repeatedly Her music alternates moments of sudden quiet with moments of dramatic intensity. Alternating current (n. Phr): an electric current that changes its direction regularly. The elecricity supplied to homes is alternating current.

4. Direct current (n.phr): electrical current which moves in one direction only Batteries are a source of direct current frequency(n): The number of repetitions per unit time of a complete waveform In the UK, AC supply alternates 50 times per second, so its frequency is 50 hertz.

5. Single phase current(n): the current which forms one sine wave. The current supplied to homes is single phase.

6. Three-phase current(n): three currents having different timing In factories and large buildings, three phase current is needed as they have powerful electrical equipment

7. generate(v): to produce sth Wind turbines generate electricity for the local community. generator(n): a machine for producing electricity The school’s generators are used during a power cut.

8. Transform(v): to change the form of sth The photochemical reactions transform the light into electrical impulses. Transformer(n): a device which changes the voltage or other characteristic of electrical energy as it moves from one circuit to another You may need a transformer if you want to run a personal stereo off alternating current.

9. Step up(phr.v): to increase the size, amount or speed of a process If we want to grow as a factory, wee need to step up the production. Step down(phr.v): to reduce the amount, supply or rate of something The doctor has said that I can start stepping down my medication in a few days' time.

10. inverter(n): a device which converts DC to AC induction(n): the process by which electrical or magnetic properties are transferred, without physical contact, from one circuit or body to another

11. Read the texts on page 13 and anwer the questions 1. What is a sine wave? 2. Why three phase current should be used in factories? 3. What is the fuction of distribution lines? 4. What is Photovaoltaic cells?How the energy is produced? 5. Why the electricty produced by PVs cannot be used at home?

12. Answers 1. The wave of AC supply that we see/use on a graph 2. Those buildings have powerful electrical equipmenrt and it provides a smoother supply as it reduces the gaps between the voltage peaks 3. It supplies electricity to streets and houses 4. PVs are solar cells, electriciy is produced from sunlight. 5. Because PVs genreate direct current, and to be used at home DC should be inverted into AC

13. Do the exercises on your study pack