Supermagnet

Scientists have achieved great success in the development of the first super strong superconducting magnet. For its size, weight, energy consumption it is the most powerful magnet ever built. Such magnets are used in dozens of laboratories throughout the world. The supermagnet creates a magnetic twice as strong as that from a conventional iron-core electromagnet. The new magnet runs from an ordinary automobile storage battery. The superconducting magnet produces a magnetic strength, or flux density, of 43000 gausses.

Scientists agree that such magnets can revolutionize almost every aspect of man’s use of electricity including the generation, distribution and use of electric power. The new magnet is wound from a wire which is a superconductor. There are materials which have the remarkable property of losing all electrical resistance at temperatures near absolute zero. Once started, supercurrents of electricity flow through superconductors forever without loss in strength.

Until a few years ago superconductors were simply a laboratory curiosity. Scientists believed that strong magnets could not be made from them because the magnetism they create by their supercurrents destroys their superconductivity. But it was demonstrated that certain superconductors retain their properties even in strong magnetic fields.

The superconducting magnet contains a halfmile of very thin wire, about 5000 turns of wire, which are wound into a coil or solenoid. The coil is immersed in a vessel of liquid helium which keeps it at a temperature near 450ْ F.

The energy required to cool the coil is only a small fraction of that needed to create a comparable magnetic field with a standard electromagnet.

Essentially, therefore, the magnet produces almost all of its super magnetism “for free”.

Задание 7.

Ответьте письменно на следующие вопросы:

1. What is the difference between ordinary magnets and supermagnets?

2. Is the magnetic field created by the supermagnet and the ordinary magnet the same or different?

3. What flux density does the supermagnet create?

4. What is the new magnet wound from?

5. Where is the coil immersed into?

6. How is super magnetism produced by the supermagnet?

Задание 8. Ответьте письменно, правдиво ли следующее утверждение? Если нет, то почему:

Most scientists are not sure that magnets can revolutionize almost every

aspect of man’s use of electricity.

Вариант № 3

Задание 1.

Перепишите следующие предложения. Определите по грамматическим признакам, какой частью речи являются слова, оформленные окончанием -s, и какую функцию это окончание выполняет, т.е. служит ли оно:

- показателем 3-го лица единственного числа в Present Indefinite;

- признаком множественного числа имени существительного;

- показателем притяжательного падежа имени существительного.

Переведите предложения на русский язык

1) The high-pass filter passes currents of high frequencies and opposes the flow of

low frequency current.

2) The insulators are in good condition.

3) The region’s main industry is oil production.

Задание 2.

Перепишите следующие предложения и переведите их, обращая внимание на особенности перевода на русский язык определений, выраженных именем существительным.

1) In this case a battery has a large current capacity.

2) The cell connection in parallel increases the current capacity.

3) The supply voltage varies with the load.

Задание 3.

Перепишите следующие предложения, содержащие разные формы сравнения, и переведите их на русский язык.

1) The shorter the wire, the less is its resistance to the current flow.

2) The ammeter is one of the most common meters.

3) This type of the circuits is more efficient one.

Задание 4.

Перепишите и письменно переведите предложения на русский язык, обращая внимание на перевод неопределенных и отрицательных местоимений.

1) Some galvanometers detect and measure currents as small as 10ֿ ¹ ¹ of an ampere per 1 mm of the scale.

2) No charges can move in an open circuit.

3) Any motion across the direction of the Faroe lines produces an e.m.f. in the conductor.

Задание 5.

Перепишите следующие предложения, определите в них видовременные формы глаголов и укажите их инфинитив; переведите предложения на русский язык.

1) The readings on the scale will show the measured value of current.

2) The conductivity increased with heating.

3) A modern ship has a rather complex electrical equipment.

Задание 6.

Перепишите и письменно переведите первые 2 абзаца текста.

Comparison of the A.C. and D.C. Circuits

In a d.c. circuit a current flows always in the same direction. In an a.c. circuit the supply terminals are continually reversing their polarity, so that the current so continual reverses its direction. In a d.c. circuit the voltage and the current being constant, there is no question of phase differ­ence between the current and the voltage. But in a.c. circuits the e.m.f. and current are nut of phase wit each other.

A current setting up a magnetic flux surrounding the con­ductor in which it flows, important effects are observed in the a.c. The magnetic flux alternates with the current and in­duces an e.m.f. in the circuit. This e.m.f. gives rise to the phase difference between the current and applied voltage. In a.c. circuits capacitance effects may be important. A capacitor, when used in a d.c. circuit, constitutes after an initial charging an open circuit through which no current flews. But with an a.c. circuit the capacitor, being continually charged and discharged in opposite directions, takes a current and in­troduces " capacitance" into the circuit.

The a.c magnetic flux set up by а.c. gives the possibility of using a transformer. It changes the voltage of the circuit as required. It is the major advantage of a.c. as compared with d.c. For the efficient transmissions of electric power over long distances, a high voltage is nесеssагу, the efficiency of transmission increasing with the increase of voltage. Since with d.c. it is much more difficult to increase the voltage, therefore the using of d.c. for transmission is limited.

With an a.c. supply a transformer can be used to transform the generated voltage to a high value, other transformers be­ing used to step down this voltage.

Задание 7.

Ответьте письменно на следующие вопросы:

1. What is the direction of a d.c. (an a.c.)?

2. Why is there a phase difference between the current and voltage in an a.c. circuit?

3. When is an e.m.f. induced in the circuit?

4. What is the main advantage of an a.c.?

5. Which current (d. or a.) changes its voltage more easily?

6. What is the voltage of current changed by?

Задание 8.

Ответьте письменно, правдиво ли следующее утверждение? Если нет, то почему:

Rather low voltage is nесеssагу for the efficient transmissions of electric power over long distances.

Вариант № 4

Задание 1.

Перепишите следующие предложения. Определите по грамматическим признакам, какой частью речи являются слова, оформленные окончанием -s, и какую функцию это окончание выполняет, т.е. служит ли оно:

- показателем 3-го лица единственного числа в Present Indefinite;

- признаком множественного числа имени существительного;

- показателем притяжательного падежа имени существительного.

Переведите предложения на русский язык

1) A transformer transfers electric energy from one electric cir­cuit to another without a change in frequency.

2) We use different meters for different purposes.

3) Scientists agree that such magnets can revolutionize almost every aspect of man’s use of electricity including the generation, distribution and use of electric power.

Задание 2.

Перепишите следующие предложения и переведите их, обращая внимание на особенности перевода на русский язык определений, выраженных именем существительным.

1) Modern electric power systems use transformers to convert electricity into different voltages.

2) The cell connection in parallel increases the current capacity.

3) There are no energy storage facilities here.

Задание 3.

Перепишите следующие предложения, содержащие разные формы сравнения, и переведите их на русский язык.

1) The best conductor has the least resistance; quite opposite, the poorest conductor has the greatest resistance.

2) That power station is the largest one in Ukraine.

3) The faster the change of current, the greater the e.m.f. that will he induced.

Задание 4.

Перепишите и письменно переведите предложения на русский язык, обращая внимание на перевод неопределенных и отрицательных местоимений.

1) No current passes through that circuit.

2) Some resistors have a constant value - these are fixed resistors.

3) Any conductor can conduct current when high enough voltage is applied to it.

Задание 5.

Перепишите следующие предложения, определите в них видовременные формы глаголов и укажите их инфинитив; переведите предложения на русский язык.

1) This engineer's experiment resulted in the design of new electric device.

2) The engineers will connect some additional elements to the circuit next time.

3) An electric cell consists of an electrolyte and two electrodes.

Задание 6.

Перепишите и письменно переведите первые 2 абзаца текста.

Rectifiers

Most power sources supply a.c. because it is easily gene­rated and transmitted over long lines. But d. currents are necessary for some industrial applications. Therefore it is fre­quently desirable to convert from a.c. to d.c. The most con­venient way to change a.c. to d.c. is by means of a rectifier. A rectifier is capable of changing a.c. into d.c. The current thus changed is called " rectified".

The basic principle of a rectifier is that it permits current to flow in one direction only. A rectifier, a diode tube, is a device consisting of two elements, one being an electron emitter or cathode, the other an electron collector or anode or plate. Since electrons in a diode can flow in one direction only, from the cathode to the anode (plate), the diode provides the unilateral conduction necessary for rectification. Since electrons are negative char­ges, they fly to the plate only when the plate is positive.

When it becomes negative, it repels the electrons back to the cathode from which they were emitted. Therefore, when a. voltage is applied to the plate, it becomes alternately positive and negative so that plate current flows only during that half of the time when the plate (anode) is positive, and only in one direction. A diode tube operating in this manner cuts off the negative halves of the a.c. cycles and is called a half-wave rectifier. In the half-wave rectifier the current flows only during the positive half-cycle of the applied a.c. voltage.

The efficiency of the half-wave rectifier is low and it is used only for applications requiring a small current.

Задание 7.

Ответьте письменно на следующие вопросы:

1. What is an a.c. necessary to convert to a d.c. for?

2. What is a current changed by?

3. What is a rectifier?

4. What are the main parts of a rectifier?

5. What direction does a current flow in a rectifier?

6. What is the charge of the cathode (anode)?

Задание 8.

Ответьте письменно, правдиво ли следующее утверждение? Если нет, то почему:

In the half-wave rectifier the current flows both during the positive and negative half-cycle of the applied a.c. voltage.

Вариант № 5

Задание 1.

Перепишите следующие предложения. Определите по грамматическим признакам, какой частью речи являются слова, оформленные окончанием -s, и какую функцию это окончание выполняет, т.е. служит ли оно:

- показателем 3-го лица единственного числа в Present Indefinite;

- признаком множественного числа имени существительного;

- показателем притяжательного падежа имени существительного.

Переведите предложения на русский язык

1) Last year we repaired our plant’s equipment.

2) What moves the coil and the pointer?

3) Electromagnets have wide application.

Задание 2.

Перепишите следующие предложения и переведите их, обращая внимание на особенности перевода на русский язык определений, выраженных именем существительным.

1) A current flow produces some effects.

2) In that case a battery has a large voltage output.

3) When the current flow is decreased, the magnetic lines of force again cut the wire.

Задание 3.

Перепишите следующие предложения, содержащие разные формы сравнения, и переведите их на русский язык.

1) The most con­venient way to change a.c. to d.c. is by means of a rectifier.

2) The more experiments we carry out, the more data we obtain.

3) This meter is about three times as sharp as that one.

Задание 4.

Перепишите и письменно переведите предложения на русский язык, обращая внимание на перевод неопределенных и отрицательных местоимений.

1) Are there any cells connected in series?

2) There are some models of diesel engines in that laboratory.

3) We used no very special devices to measure the value of resistance.

Задание 5.

Перепишите следующие предложения, определите в них видовременные формы глаголов и укажите их инфинитив; переведите предложения на русский язык.

1) The radio station informed us about bad weather condition in the North Sea.

2) The real training of an electrical engineer begins on board ship.

3) Two parallel conductors forming an electric circuit will have a comparatively small self-inductance.

Задание 6.

Перепишите и письменно переведите первые 2 абзаца текста.

Types of Inductance

An electric circuit, in which an e.m.f. is induced while a current is changing in this circuit, is called an inductive circuit and this circuit has, self-inductance. So the circuit, in which a change of current causes an e.m.f. to be induced within the circuit itself, possesses inductance or self-inductance. Self-inductance is the ability of a circuit to produce an e.m.f. in the same circuit in which the current is changing. Self-inductance is caused by variations in the magnetic field up by the varying current itself. Two parallel conductors forming an electric circuit will have a comparatively small self-inductance. But a solenoid will have a large self-inductance since there will be a considerable magnetic field linked with the solenoid.

When the e.m.f. is induced into a circuit by a change of flux, or in other wоrds when the e.m.f. is produced by a current changing in an adjacent circuit, this property of a circuit is called mutual inductance.

Mutual inductance is the property of a circuit to produce an e.m.f. in a near-by circuit by induction when the current in the first circuit changes. The second circuit can also induce an e.m.f. in the first when the current in the second changes. Mutual inductance is the ability not only of the circuits but of coils as well. Mutual inductance is the common property of two associated electric circuits or two coils and is the same in both directions.

Both self-inductance and mutual inductance occur only when there is a change in current.

Задание 7.

Ответьте письменно на следующие вопросы:

1. When is an e.m.f. induced in a circuit?

2. What is self-induction?

3. What is self-inductance caused by?

4. What is mutual inductance?

5. When do two coils have mutual inductance?

6. Due to what is an e.m.f. induced in one of the two paral­lel coils?

Задание 8.

Ответьте письменно, правдиво ли следующее утверждение? Если нет, то почему:

Only mutual inductance occurs when there is a change in current.