IV. Match (21-30) with their definitions (A-L). There are two definitions that you do not need to use.

21.	chamber	A.	reach a destination, either real or abstract
22.	uniform	B.	the place where something begins
23.	voltage	C.	change to the contrary
24.	source	D.	the number of occurrences within a given time period
25.	ion	E.	a relation between two opposite attributes or tendencies
26.	frequency	F.	an atom or molecule or group that has lost or gained one or more electrons
27.	reversing	G.	direct or control; projects, businesses
28.	to operate	H.	showing a single form or character in all occurrences
29.	to gain	I.	the rate at which energy is drawn from a source that produces a flow of electricity in a circuit
30.	polarity	J.	a natural or artificial enclosed space
		K.	a very small piece of something
		L.	the scientific study of natural forces, such as energy, heat, light, etc

Supplementary Tasks :

I. For statements (1-10) choose the best alternative (A, B or C) to replace the expressions in italics:

1. An ion sourse is located at the centre of an evacuated chamber ... (line 8)

A.installedB.orientedC.discovered

2. ...an electromagnet that creates a uniform field ...(line 10)

A.prepares B. makes C.induces

3. ... an oscillator that operates at the frequency equal to ... (line 13)

A.actsB.worksC.behaves

4. The electric fields caused by this accelerating voltage are concentrated in the gap between the dees ...(line 15)

A.blankB.apertureC.pause

5. Some means of focusing is required ...(line 21)

A.compelled B. asked C.needed

6. ... this focusing is supplied by the accelerating electric fields ... (line 23)

A. provided B. furnished C. added

7. ... after the particle has gained significant energy ... (line 24)

A.mainB.goodC.considerable

8. The energy gained by a particle in a classical cyclotron ...(line 27)

A.doneB.achievedC.travelled

9. The highest energy imparted to protons in a classical cyclotron ... (line 31)

A.transmitted B. ceded C. received

10. ... this achievement requires the imposition of hundreds of kilovolts ... (line 32)

A.fact B. event C.attainment

II. Determine the key message of the text. Choose the best alternative (A, B, C, D or E):

A. A uniformmagnetic field is created by an ion source.

B. A uniform magnetic field is created in classical cyclotrons.

C. The principle of work in classical cyclotrons is given.

D. To gain some energy a particle requires the imposion of hundreds of kilovolts to the dees.

E. Classical cyclotrons work due to the isochronicity of the orbits of ions in a uniform magnetic field.

TEXT 13

THE CHARGED WORLD

(1)It would be hard to imagine the world without electricity. Not only is it the energy that powers everything from toasters to televisions, but it is one of the fundamental forces in the Universe that holds all matter together. (2)Yet until the late 18^th century scientists knew almost nothing about electricity. The ancient Greeks knew that when you rubbed a kind of resin called amber with cloth it attracts fluff. The word “electricity” comes from “elektron”, the Greek word for amber. For thousands of years amber attraction was considered a minor curiosity. (3)In the 18^th century scientists such as the French chemist Charles Dufay and English physicist Stephen Gray began to investigate electricity. They soon discovered, not only that various substances could conduct the same attraction to fluff as amber, but also that rubbing two similar substances together made them repel each other, not attract. This attraction and repulsion came to be called positive and negative electrical "charge". (4)By the mid-1700s some machines could generate quite large charges when a handle was turned to rub glass on sulphur. The charge could even be stored in a special glass jar called a Leyden jar – then suddenly let out via a metal chain to create a spark. Seeing these sparks, American statesman and inventor Benjamin Franklin wondered if they were the same as lightning. He attached a metal chain like that of a Leyden jar to a kite sent up in a thunderstorm. The lightning sent a spark from the chain – only much bigger than expected – and Franklin was lucky to survive. People were so excited by Franklin’s discovery that demonstrations of electrical effects became very fashionable. (5)The real breakthrough, however, was the discovery of the link between electricity and magnetism. In 1819 Danish physicist Hans Orsted suggested that an electrical current has a magnetic effect, turning the needle of compass. Little more than a decade later Joseph Henry in America and Michael Faraday in Britain proved that the opposite is in fact true – that is actually a magnet that has an electrical effect. When a magnet is moved near an electric circuit, it generates a surge of electricity in the circuit. Using this principle – called electromagnetic induction – huge machines could be built to generate large quantities of electricity.