Модуль 1 - Общие сведения, глаголы to be, to have, конструкция there is(are), времена группы Indefinite Active Voice (1096805), страница 10
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The three main particlesmaking up an atom are the proton, the neutron and the electron.Electrons spin around the center, or nucleus, of atoms, in the same way the moon spins around the earth.The nucleus is made up of neutrons and protons.Electrons contain a negative charge, protons a positive charge. Neutrons are neutral – they have neither apositive nor a negative charge.42There are many different kinds of atoms, one for each type of element.
An atom is a single part that makesup an element. There are 118 different known elements that make up every thing! Some elements likeoxygen we breathe are essential to life.Each atom has a specific number of electrons, protons and neutrons. But no matter how many particles anatom has, the number of electrons usually needs to be the same as the number of protons.
If the numbersare the same, the atom is called balanced, and it is very stable.So, if an atom had six protons, it should also have six electrons. The element with six protons and sixelectrons is called carbon. Carbon is found in abundance in the sun, stars, comets, atmospheres of mostplanets, and the food we eat.
Coal is made of carbon; so are diamonds.Some kinds of atoms have loosely attached electrons. An atom that loses electrons has more protons thanelectrons and is positively charged. An atom that gains electrons has more negative particles and isnegatively charge. A "charged" atom is called an "ion."Electrons can be made to move from one atom to another.
When those electrons move between the atoms,a current of electricity is created. The electrons move from one atom to another in a "flow." One electron isattached and another electron is lost.This chain is similar to the fire fighter's bucket brigades in olden times. But instead of passing one bucketfrom the start of the line of people to the other end, each person would have a bucket of water to pour fromone bucket to another. The result was a lot of spilled water and not enough water to douse the fire. It is asituation that's very similar to electricity passing along a wire and a circuit.
The charge is passed from atomto atom when electricity is "passed."Scientists and engineers have learned many ways to move electrons off of atoms. That means that whenyou add up the electrons and protons, you would wind up with one more proton instead of being balanced.Since all atoms want to be balanced, the atom that has been "unbalanced" will look for a free electron tofill the place of the missing one. We say that this unbalanced atom has a "positive charge" (+) because ithas too many protons.Since it got kicked off, the free electron moves around waiting for an unbalanced atom to give it a home.The free electron charge is negative, and has no proton to balance it out, so we say that it has a "negativecharge" (-).So what do positive and negative charges have to do with electricity?Scientists and engineers have found several ways to create large numbers of positive atoms and freenegative electrons. Since positive atoms want negative electrons so they can be balanced, they have astrong attraction for the electrons.
The electrons also want to be part of a balanced atom, so they have astrong attraction to the positive atoms. So, the positive attracts the negative to balance out.The more positive atoms or negative electrons you have, the stronger the attraction for the other. Since wehave both positive and negative charged groups attracted to each other, we call the total attraction"charge."Energy also can be measured in joules. Joules sounds exactly like the word jewels, as in diamonds andemeralds. A thousand joules is equal to a British thermal unit.When electrons move among the atoms of matter, a current of electricity is created.
This is what happensin a piece of wire. The electrons are passed from atom to atom, creating an electrical current from one endto other, just like in the picture.Electricity is conducted through some things better than others do. Its resistance measures how wellsomething conducts electricity. Some things hold their electrons very tightly. Electrons do not movethrough them very well. These things are called insulators. Rubber, plastic, cloth, glass and dry air aregood insulators and have very high resistance.43Other materials have some loosely held electrons, which move through them very easily. These are calledconductors. Most metals – like copper, aluminum or steel – are good conductors.Where Does the Word 'Electricity' Come From?Electrons, electricity, electronic and other words that begin with "electr..." all originate from the Greekword "elektor," meaning "beaming sun." In Greek, "elektron" is the word for amber.Amber is a very pretty goldish brown "stone" that sparkles orange and yellow in sunlight.
Amber isactually fossilized tree sap! It's the stuff used in the movie "Jurassic Park." Millions of years ago insectsgot stuck in the tree sap. Small insects which had bitten the dinosaurs, had blood with DNA from thedinosaurs in the insect's bodies, which were now fossilized in the amber.Ancient Greeks discovered that amber behaved oddly - like attracting feathers - when rubbed by fur orother objects.
They didn't know what it was that caused this phenomenon. But the Greeks had discoveredone of the first examples of static electricity.The Latin word, electricus, means to "produce from amber by friction."So, we get our English word electricity from Greek and Latin words that were about amber.3. Resistance and Static ElectricityAs we have learned, some kinds of atoms contain loosely attachedelectrons. Electrons can be made to move easily from one atom to another.When those electrons move among the atoms of matter, a current ofelectricity is created.Take a piece of wire.
The electrons are passed from atom to atom, creatingan electrical current from one end to the other. Electrons are very, verysmall. A single copper penny contains more than10,000,000,000,000,000,000,000 (1x1022) electrons.Electricity "flows" or moves through some things better than others do.
Themeasurement of how well something conducts electricity is called its resistance.Resistance in wire depends on how thick and how long it is, and what it's made of. The thickness of wire iscalled its gauge. The smaller the gauge, the bigger the wire. Some of the largest thicknesses of regular wireis gauge 1.Different types of metal are used in making wire. You can have copper wire, aluminum wire, even steelwire. Each of these metals has a different resistance; how well the metal conducts electricity.
The lower theresistance of a wire, the better it conducts electricity.Copper is used in many wires because it has a lower resistance than many other metals. The wires in yourwalls, inside your lamps and elsewhere are usually copper.A piece of metal can be made to act like a heater. When an electrical current occurs, the resistance causesfriction and the friction causes heat. The higher the resistance, the hotter it can get. So, a coiled wire highin resistance, like the wire in a hair dryer, can be very hot.44Some things conduct electricity very poorly.
These are called insulators. Rubber is a good insulator, andthat's why rubber is used to cover wires in an electric cord. Glass is another good insulator. If you look atthe end of a power line, you'll see that it is attached to some bumpy looking things. These are glassinsulators.
They keep the metal of the wires from touching the metal of the towers.Static ElectricityAnother type of electrical energy is static electricity. Unlike current electricity that moves, static electricitystays in one place.Try this experiment...Rub a balloon filled with air on a wool sweater or on your hair. Then hold it up to a wall. The balloon willstay there by itself.Tie strings to the ends of two balloons.
Now rub the two balloons together, hold them by strings at the endand put them next to each other. They'll move apart.Rubbing the balloons gives them static electricity. When you rub the balloon it picks up extra electronsfrom the sweater or your hair and becomes slightly negatively charged.The negative charges in the single balloon are attracted to the positive charges in the wall.The two balloons hanging by strings both have negative charges.
Negative charges always repel negativecharges and positive always repels positive charges. So, the two balloons' negative charges "push" eachother apart.Static electricity can also give you a shock. If you walk across a carpet, shuffling your feet and touchingsomething made of metal, a spark can jump between you and the metal object. Shuffling your feet picks upadditional electrons spread over your body. When you touch a metal doorknob or something with apositive charge the electricity jumps across the small gap from your fingers just before you touch the metalknob.
If you walk across a carpet and touch a computer case, you can damage the computer.One other type of static electricity is very spectacular. It's the lightning in a thunder and lightning storm.Clouds become negatively charged as ice crystals inside the clouds rub up against each other. Meanwhile,on the ground, the positive charge increases. The clouds get so highly charged that the electrons jump from45the ground to the cloud, or from one cloud to another cloud. This causes a huge spark of static electricity inthe sky that we call lightning.But What Is Static Electricity?As far as you remember the word "electricity" came from the Greek words "elektor," for "beaming sun"and "elektron," both words describing amber.
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