The conducting materials give green light to electrons which move from one atom to another when the potential difference is applied across them. This flow of electrons in a closed circuit is called current. On the basis of the direction of movement of electrons in a closed circuit, the electric current is mainly classified into two types, i.e., the alternating current and the direct current. The current which changes its direction at a regular interval of time such type of current is called alternating current. Direct current is unidirectional or flows only in one direction.
The charges in the alternating current flow either by rotating a coil in the magnetic field or by rotating a magnetic field within a stationary coil. In direct current, the charges flow by keeping the constant magnetism along the wire.
The frequency of the alternating current give or take 50 to 60 hertz depends on the country standard, whereas the frequency of the direct current always remains zero.
The power factor of the alternating current lies between zero to one, whereas the power factor of the direct current always remains one.
The alternating current can be graphically represented through different irregular wave shape such as triangular wave, square wave, periodic wave, the saw-tooth wave, sine wave, etc. The direct current is graphically represented by the straight line.
The alternating current transmits over a long distance with some losses, whereas the direct current transmits over very long distances with negligible losses.
The alternating current is converted into direct current with the help of rectifier whereas the direct current is converted into alternating current with the help of the inverter.
Few substations require for the generation and transmission of the alternating current. Extra substations require for the transmission of direct current.
The alternating current is used in industries, factories, and for the household purposes. The direct current is mainly used in electronic equipment, flash lighting, hybrid vehicles, electroplating, electrolysis, for exciting the field winding of the rotor, etc.
1. Заполните пропуски в словосочетаниях:
rotating a in the field
hybrid
used in electronic
the of of in a closed circuit
wave, wave, periodic
2. Продолжите условные предложения:
1. If the current changes its directions periodically, it …
2. If the electric charge inside the conductor flew in one direction, it …
3. If the load on a three-phase system had been balanced equally among the phases, …
4. If alternating current systems could use transformers, they …
5. If an Italian scientist hadn’t developed AC generators and transformers, …
3. Выпишите из текста предложения, содержащие герундий / герундиальный оборот.
4. Найдите в тексте английские идиомы, выпишите и переведите их.
1.If Mary comes to my house, we will play football.
2.If Ann doesn't come to my house, I will read a book
3.if they have their holidays in summer, they will go to the seaside
4.If the fog thickens, Harold will put up the tent for the nigh
5.When Nick finishes his work, he will go to the theatre
6.I will buy this game, if our father gives me money
7. When we come to your place, you will show us your present
8. I will wait for my friend until he comes from the shop.
№2
1. If I were you, I would get a new job.
2. If he were younger, he would travel more.
3. If we weren`t friends, I be angry with you.
4. If I had enough money, I would buy a big house.
5. If she weren't always so late, she would be promoted.
6. She would be happier if she had more friends.
7. We would buy a house if we decided to stay here.
8. They would have more money if they didn't buy so many clothes
9. We would come to dinner if we had time.
10. She would call him if she knew his number.
№3
1. If he were slim, he would be more attractive.
2. If I weren't busy, i would pick the children up.
3. If you drank much wine, you would feel sleepy.
4. if I were married, I would have lunch at home.
5. If Peter lived in a house, he would have a dog.
In 1990 Tatarstan has ceased to be autonomous. So It was decided to take a temorary flag of Tatar community center. During the year, comission had been developing national symbols. The white moon and star adorn the flag, which is divided by a diagonal, combining shades of red and green colours.
On the 29th of November,1991, by the decision of the Supreme Council, the flag became national symbol of Tatar Republic. It was a quite long way to set the present flag.