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implement this on a global scale, to provide "free" energy which could be tapped by any appropriate receiver. He believed this used a non-Hertzian electromagnetic wave which could propagate through the earth at faster than the speed of light.

In the years following 1904, Tesla turned to pioneering and patenting a very efficient form of turbine. The materials of the day could not stand the stresses, and it was never fully exploited.

Tesla was awarded the Edison Medal by the American Institute of Electrical Engineers in 1917, which he reluctantly accepted on the insistence of his contemporaries. He also received numerous doctoral degrees.

The rest of his life was spent in New York, living in relative obscurity. He continued to do a small amount of research and wrote magazine articles containing various revelations and predictions, such as a "death ray" which would prevent all wars, his own dynamic theory of gravity, and interplanetary communication systems. In January 1943, at age 86, he died with no will and few possessions.

It is an enigma that such a pioneer in many fields, with well over 100 patents to his name, is not better known today. In most electrical engineering or radio text books he is not even mentioned, despite the fact he was a definite innovator in these areas. Nikola Tesla was an inventor and engineer, always practical, and not a mathematical theoretician. Some of his ideas have not been generally accepted by academics, and so he has not been given the recognition he truly deserves.

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ELECTRICITY QUIZ

1.Simple device that generates electricity. [4 letters]

2.The metal or graphite rod in an electric cell. [9]

3.Instrument for measuring potential difference or voltage. [9]

4.Substance that does not allow electrons to pass through. [9]

5.A screwdriver placed across two wires in a circuit creates a …circuit. [5]

6.Instrument to measure current. [7]

7.Type of electricity produced by rubbing plastic on wool. [6]

8.Substance that allows electrons to pass through easily. [9]

9.DC stands for …Current. [6]

10.Device that increases or decreases voltage. [11]

11.Household circuits are of this type. [8]

12.Voltage divided by current is the …. [10]

13.Wire that discharges excess electricity to the earth. [5]

14.Protective device which "blows" if there is excess electricity in a house circuit. [4]

15.Unit of potential difference or voltage. [4]

16.Unit of resistance. [3]

17.Current electricity is a flow of …along a wire. [9]

18.A series of cells. [7]

19.Circuit where components are placed one after the other. [6]

20.Unit of current. [6]

21.AC stands for Alternating …. [7]

22.Solution in an electric cell. [11]

23.Making of electricity is called electricity …. [10]

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All electrical phenomena are alike in that that arise from the presence

or motion of charge. Most practical electrical devices are based on the motion of charge around a complete circuit, so that the charge can be recycled and does not hit any dead ends. The most useful measure of the flow of charge is current,

I = q/ t.

An electrical device whose job is to transform energy from one form into another, e. g., a lightbulb, uses power at a rate which depends both on how rapidly charge is flowing through it and on how much work is done on each unit of charge. The latter quantity is known as the voltage difference between the point where the current enters the device and the point where the current leaves it. Since there is a type of potential energy associated with electrical forces, the

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amount of work they do is equal to the difference in potential energy between the two points, and we therefore define voltage differences directly in terms of potential energy, V = PEelec/q. The rate of power dissipation is P = I V.

Many important electrical phenomena can only be explained if we understand the mechanisms of current flow at the atomic level. In metals, currents are carried by electrons, in liquids by ions. Gases are normally poor conductors unless their atoms are subjected to such intense electrical forces that the atoms become ionized.

Many substances, including all solids, respond to electrical forces in such a way that the flow of current between two points is proportional to the voltage difference between those points. Such a substance is called ohmic, and an object made out of an ohmic substance can be rated in terms of its resistance,

R = V/I. An important corollary is that a perfect conductor, with R = 0, must have constant voltage everywhere within it.

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PROBLEM SOLVING

1. A hydrogen atom consists of an electron and a proton. For our present purposes, we‘ll think of the electron as orbiting in a circle around the proton. The subatomic particles called muons behave exactly like electrons, except that a muon‘s mass is greater by a factor of 206.77. Muons are continually bombarding the Earth as part of the stream of particles from space known as cosmic rays. When a muon strikes an atom, it can displace one of its electrons. If the atom happens to be a hydrogen atom, then the muon takes up an orbit that is on the average 206.77 times closer to the proton than the orbit of the ejected electron. How many times greater is the electric force experienced by the muon than that previously felt by the electron?

2. A resistor has a voltage difference V across it, causing a current I to flow. a) Find an equation for the power it dissipates as heat in terms of the variables I and R only, eliminating V.

b) If an electrical line coming to your house is to carry a given amount of current, interpret your equation from part (a) to explain whether the wire‘s resistance should be small, or large.

3. If a typical light bulb draws about 900 mA from a 110-V household circuit, what is its resistance? (Don‘t worry about the fact that it‘s alternating current.)

4.In a wire carrying a current of 1.0 pA, how long do you have to wait, on the average, for the next electron to pass a given point? Express your answer in units of microseconds.

5.You have to do different things with a circuit to measure current than to measure a voltage difference. Which would be more practical for a printed circuit board, in which the wires are actually strips of metal embedded inside the board?

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SELF-CHECK

І. Radioactivity.

1. Write the letter of the term that best matches each definition:

1)Nuclear radiation in the form of electromagnetic waves with a very short wavelength. ___

2)An instrument that detects radioactivity by way of an electric current. ___

3)The release of streams of particles or energy from the nuclei of atoms of certain elements. ___

4)A positive particle consisting of two protons and two neutrons. ___

5)The splitting of a nucleus with a large mass into two nuclei with smaller masses. ___

6)The joining of several nuclei with smaller masses into one nucleus with a large mass. ___

7)The change of one element into another by the release of radiation from atoms of the element. ___

8)A container in which radioactive particles are detected by the trails (сліди) they leave behind. ___

2. Select the letter of the answer that best completes each of the following:

9)Becquerel detected radioactivity by using …

a.a Geiger counter

b.photographic film

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c.an electroscope

d.a nuclear reactor.

10) Beta particles are …

a.electromagnetic waves

b.positively charged

c.negatively charged

d.neutral.

11) Gamma rays can be stopped by …

a.thick lead

b.thin aluminium foil

c.paper

d.cardboard

12) The sun produces energy by …

a.nuclear breakdown

b.nuclear fusion

c.radioactive decay

d.nuclear fission.

13) Unstable nuclei often have …

a.an equal number of protons and neutrons

b.no neutrons

c.more neutrons than protons

d.no protons

3. Complete the following:

14) Three forms of radiation that have been identified from radioactive elements are ….

15) Radioactive isotopes continue to decay until they become ….

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II. The Atom.

1. Write the letter of the term that best matches each definition:

16)A space from which all matter has been removed. ___

17)Metal strips at each end of a vacuum tube. ___

18)Number of protons in nucleus of atom. ___

19)An electron that has absorbed energy and moved farther from the nucleus._

20)Positively charged particle in nucleus of atom. ___

21)Atoms of same element with different masses. ___

22)Sum of protons and neutrons of atom. ___

23)The average of the masses of all the atoms of an element. ___

2. Select the letter of the answer that best completes each of the following:

24) In Thomson‘s ―raisin cookie‖ model of the atom, the particles that were scattered (розсіюватися, розбігатися) like plums in a pudding were …

a.electrons

b.protons

c.neutrons

d.alpha particles.

25) Aluminium has an atomic number of 13 and a mass number of 27. The number of neutrons in aluminium is …

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26) The maximum number of electrons in the outermost (найвіддаленіший від центру) energy level of an atom is …

a.2

b.4

c.6

d.8.

27) An atom has the same number of electrons as its …

a.atomic number

b.atomic mass

c.mass number

d.isotopes.

3. Complete the following:

28) Based on the results of his gold foil experiment, Rutherford proposed that most of the atom‘s mass is in a positively charged ….

29) The atomic mass of an element is not usually a whole number because it is an …of the masses of all the isotopes of the element.

30) Elements usually react with each other only when the outer energy levels of their atoms are not ….

III. Electricity.

1. Write the letter of the term that best matches each definition:

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