2_kurs_4_semestr

PROBLEM SOLVING

1.A helium atom finds itself momentarily in this arrangement. Find the direction and magnitude of the force acting on the righthand electron. The two protons in the nucleus are so close together (~ 1 fm) that you can consider them as being right on top of each other.

2.Suppose you are holding your hands in front of you, 10 cm apart.

(a) Estimate the total number of electrons in each hand.

(b) Estimate the total repulsive force of all the electrons in one hand on all the electrons in the other.

(c)Why don‘t you feel your hands repelling each other?

(d)Estimate how much the charge of a proton could differ in magnitude from the charge of an electron without creating a noticeable force between your hands.

3. The reaction is p + e‒ → n + v.

(a) Show that charge is conserved in this reaction.

(b) Explain why electron capture doesn‘t occur in hydrogen atoms. (If it did, matter wouldn‘t exist!)

4. 234Pu decays either by electron decay or by alpha decay. (A given 234Pu nucleus may do either one; it‘s random.) What are the isotopes created as products of these two modes of decay?

42

CHAPTER II. ELECTRICITY

UNIT 8

Electricity

Read the text and be ready to answer the teacher‟s questions.

Answer the following questions:

1)What is electricity?

2)What does it mean to be an energy carrier?

3)Can electricity be renewable or non-renewable?

4)What was before the invention of electricity?

5)Who has worked at electricity? What have they invented?

Electricity is the flow of electrical power or charge. It is both a basic part of nature and one of our most widely used forms of energy.

Electricity is actually a secondary energy source, also referred to as an energy carrier. That means that we get electricity from the conversion of other sources of energy, such as coal, nuclear, or solar energy. These are called primary sources. The energy sources we use to make electricity can be renewable or non-renewable, but

electricity itself is neither renewable nor nonrenewable.

43

Before electricity became available over 100 years ago, houses were lit with kerosene lamps, food was cooled in iceboxes, and rooms were warmed by wood-burning or coal-burning stoves.

Many scientists and inventors have worked to decipher the principles of electricity since the 1600s. Some notable accomplishments were made by Benjamin Franklin, Thomas Edison, and Nikola Tesla.

Benjamin Franklin demonstrated that lightning is electricity. Thomas Edison invented the first long-lasting incandescent light bulb.

Prior to 1879, direct current (DC) electricity had been used in arc lights for outdoor lighting. In the late 1800s, Nikola Tesla pioneered the generation, transmission, and use of alternating current (AC) electricity, which reduced the cost of transmitting electricity over long distances. Tesla‘s inventions used electricity to bring indoor lighting to our homes and to power industrial machines.

Despite its great importance in our daily lives, few of us probably stop to think what life would be like without electricity. Like air and water, we tend to take electricity for granted. But we use electricity to do many jobs for us every day — from lighting, heating, and cooling our homes to powering our televisions and computers.

Describe what electricity is, in your own words.

Most electrical wire is covered in a rubber or plastic coating called insulation. What is the purpose of having this “insulation” covering the metal wire?

What is the difference between materials classified as conductors versus those classified as insulators, in the electrical sense of these words? Identify several substances that are good conductors of electricity, and several substances that are good insulators of electricity.

44

GRAMMAR

Modal Verbs

В англійській мові є дієслова (can, may, must, ought, should, shall, will, would, need, dare), які не мають основних форм, властивих іншим дієсловам, не виражають дії або стану, а лише необхідність, можливість,

бажаність, сумнів, дозвіл, заборону, здатність виконання дії, позначеної інфінітивом, який стоїть після них. Такі дієслова називаються

модальними.

Модальні дієслова вирізняються такими особливостями:

а) Інфінітив після них вживається без частки to (крім to have to, to be ought to, ought to, а також need і dare, після яких інфінітив може вживатися як із часткою to так і без неї).

б) Модальні дієслова не мають трьох форм, властивих іншим дієсловам.

в) У третій особі однини у Present Indefinite модальні дієслова не мають закінчення –(e)s.

г) У питальних реченнях модальні дієслова не використовують допоміжних дієслів, а самі ставляться перед підметом (крім to have to).

Can – Could – Be able to (ability)

Can expresses ability and can‟t expresses lack of ability in the present.

e.g. Kate can speak a foreign language. Tim can’t play the piano.

Could expresses general ability in the past.

e.g. Alan could sing very well when he was young. (But now he can‘t.)

45

Was/Were able to (managed to do) expresses ability that we had in the past in a particular situation. It shows that someone did something but with effort.

e.g. It was a very difficult test, but Meryl was able to answer all the questions. (She managed to answer all the questions.)

Couldn‟t expresses lack of ability in the past, either generally or in a particular situation.

e.g. My little brother couldn’t ride a bicycle when he was two. (Generally, not in a particular situation.)

Helen tried but she couldn’t open the door. (She didn‘t manage to open the door – lack of ability in a particular situation.)

We use could (not was/were able to) with the verbs see, hear, feel, smell, taste, understand, remember, guess, etc.

e.g. Marian could feel that something was wrong the moment she entered the room. (NOT: Marian was able to feel that …)

Can has only present and past tenses. We use be able to to form all the other tenses (future simple, present perfect, etc.)

e.g. I hope I’ll be able to take you out to dinner next week.

We also use can and could to:

ask for permission. Could is more formal and polite than can. Can I play with your toy?

Could you say something?

make a request. Could is more polite than can. Can you explain this word to me, please?

Could you find these people‘s phone numbers, please?

make a suggestion.

We can/could visit the museum tomorrow morning.

46

Ствердження/заперечення

1. Fill in the gaps with can/can’t, could/couldn’t or was/were able to.

1.When I arrived, I …could… see a few people waiting for the train.

2.After saving their money for ten years, they … buy a house.

3.Sam and Beth … speak Italian fluently, can‘t they?

4.… you tie your shoelaces when you were four years old?

47

5.It was a very tricky question, but Paul … answer it.

6.I …hear what they were saying because the music was too loud.

7.Although it was difficult, the children …build a tree house.

8.Susan …come to the phone. She‘s busy.

48

3. What do can and could express in each sentence?

1.We can watch the new show on TV. (suggestion)

2.It was cold last Saturday so we couldn’t go on a picnic.

3.Can I go camping with my friends at the weekend?

4.If you are not feeling well, you could stay at home.

5.Could you shut the window, please?

6.Could I speak to you for a moment, please?

7.Can you call Greg and tell him I‘ll be late?

4. Translate into English.

1.Я можу написати твір за дві години.

2.Мій старший брат вміє грати на гітарі.

3.Я не зміг відповісти на його запитання.

4.Не може бути, щоб вона не чекала нас.

5.Невже він не склав іспит?

6.Ти зможеш прийти на мій день народження?

7.Можу я взяти твій конспект з хімії?

8.Ми не змогли купити квитки на премʼєру у нашому театрі.

9.Невже вони виїхали в Канаду?

10.Твоя сестра не вміє плавати, чи не так?

49

UNIT 9

Types of Electricity

Read the text and be ready to discuss the given information.

There are two types of Electricity, Static Electricity and Current Electricity. Static Electricity is made by rubbing together two or more objects and making friction while Current Electricity is the flow of electric charge across an electrical field.

Static Electricity

Static electricity is when electrical charges build up on the surface of a material. It is usually caused by rubbing materials together. The result of a build-up of static electricity is that

objects may be attracted to each other or may even cause a spark to jump from one to the other. For example rub a balloon on wool and hold it up to the wall.

Before rubbing, like all materials, the balloons and the wool sweater have a neutral charge. This is

because they each have an equal number of positively charged subatomic particles (protons) and negatively charged subatomic particles (electrons). When you rub the balloon with the wool sweater, electrons are transferred from the wool to the rubber because of differences in the attraction of the two materials for electrons. The balloon becomes negatively charged because it gains electrons from the wool, and the wool becomes positively charged because it loses electrons.

50