III. Ответьте на следующие вопросы, пользуясь информацией из текста

1. What does the quantity of electricity in a conductor depend on?

2. What devices can be characterized by EMF?

3. How is the current driven in most circuits?

4. What is the difference between the sources of EMF for voltaic cell and for the power company?

5. How is the counter-electromotive force caused?

6. What is back EMF?

7. What happens in a generator using a rotating armature?

IV. Найдите неправильные утверждения и исправьте их

1. EMF moves electricity in a conductor.

2. Electromagnetic induction is the source of EMF for a voltage cell.

3. Back EMF occurs only in electronic devices.

4. Counter EMF is developed by an alternating or pulsating current.

5. Any motor is efficient with no friction.

V. Дополните следующие предложения фактами из текста

1. The quantity that passes any point depends on …

2. Electricity may be regarded as …

3. The net EMF for resistors is …

4. Electromagnetic induction is more extended than …

5. The CEMF is the voltage that …

VI. Подберите подходящее прилагательное к следующим существительным

Pipe , level , pole , charge , field , force , current , armature

VII. Задайте все возможные виды вопросов на основе следующих предложений

1. If the pipes are choked with dirt, they will not deliver the necessary amount of water.

2. In most circuits current is driven by a so-called "source of emf".

3. A voltaic cell can be thought of as two "surface pumps" of atomic dimension.

4. One practical application is to use this phenomenon to indirectly measure motor speed and position.

5. The voltage's polarity is at every moment the reverse of the input voltage.

VIII. Определите, какой частью речи являются неличные формы в следующих предложениях. Переведите предложения на русский язык

1. In a generator using a rotating armature and in the presence of a magnetic flux, the conductors cut the magnetic field lines as they rotate.

2. The current flowing into the motor coils is reduced.

3. The analogy of the water pipes will be useful in explaining the nature of electromotive force.

4. The net emf for that device is the energy gained per unit charge.

5. CEMF is caused by a changing electromagnetic field.

IX. Прокомментируйте ту часть текста, которая показалась вам наиболее интересной

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Прочитайте текст и определите, является ли утверждение верным

The quantity of electricity can easily be measured because the absolute unit of current is well known.

Unit Of Magnetic Force

The pole of a magnet either of the bar or solenoidal form exerts a repellent or attractive force upon the pole of another magnet according as the poles concerned are like or unlike. Advantage is taken of this fact for the measurement of magnetic forces. Thus a pole is said to be a unit pole, or to possess a unit of magnetic force, when it exerts a force of one dyne upon a similar pole placed at a distance of one centimeter from it.

This may be measured by its magnetic effect upon a unit pole under specified conditions; thus if a current passing along a conductor, one centimeter in length and bent into an arc of a circle of one centimeter radius, exerts a force of one dyne upon a unit pole placed at the centre, the current is said to be one absolute unit of current.

The absolute unit current is considered to be too large for practical purposes, and in consequence the practical unit has been taken as 1/10 of the absolute unit. This is called the Ampere. The ampere is represented practically by the current which, when passed through a solution of nitrate of silver, in accordance with a definite specification, deposits silver at the rate of 0.00118 gramme per second. The ampere does not give an idea of the quantity of electricity passing through a conductor, but serves more as a gauge to indicate the size or volume, so to speak, of a current. The quantity of electricity is given by multiplying the current by the time during which it flows, and an unit quantity of electricity is said to pass any point in a conductor when one ampere flows for one second. This unit of quantity, which is called a Coulomb, is rarely made use of in practice, but serves by inference to indicate the value of an ampere. An analogy may be drawn between the flowing of water through pipes and the passage of current through a conductor. In the former case the water has a certain definite volume per unit length of pipe; but no idea of the quantity of water delivered by the pipe is obtained until the number of such volumes which have flowed through the pipe in a definite time is known. So with a current flowing in a conductor, no idea of the quantity of electricity can be formed until the time during which it flows is taken into consideration.

Lesson 6 Voltage and Current I. Прочитайте и запомните следующие слова и словосочетания faucet 1)вентиль, втулка; 2) водопроводный кран weak слабый to illustrate 1) иллюстрировать; 2) служить примером pipe 1) труба; 2)трубопровод; 3) магистраль to remain оставаться, пребывать в прежнем состоянии или на том же месте flashlight 1) проблесковый огонь; 2) импульсная лампа, фотовспышка; 3) карманный электрический фонарь bulb 1) баллон, колба ; 2) шарик термометра internal внутренний II. Прочитайте и переведите текст Voltage and Current
Voltage Everyone uses this term, even though they might not understand it. You probably know that a single cell from a flashlight creates an electrical force of 1.5 Volts. You also know that a transistor radio battery (with the snaps on the top) creates an electrical force of 9 Volts. (There are six little cells of 1.5 Volts each inside of the 9 Volt battery.) You know that household electrical outlets are 110 or 120 Volts, and you know that "High Voltage" is dangerous. What else should you know about voltage? Again, lets look at the atomic level.  Electrons don't move from atom to atom without a reason. When electrons are flowing, there is an electrical force somewhere, pushing them along. In older text books, you might see references to ElectroMotive Force, or "EMF". We usually refer to this force as "Voltage".     This picture illustrates a single cell pocket flashlight. The 1.5 Volt cell is pushing the electrons through the bulb and the wire. Without this push, the electrons would be happy to remain stationary. In this case, chemical action within the battery causes the push. When the battery gets old, its chemical reaction slows down and its internal push gets weaker and weaker.
Current.Again, everyone uses this term without really knowing what it means. In very simple terms, current is the flow rate of the electrons in the circuit. How is that electrons would be happy to remain stationary.In this case, chemical action within the battery causes the push. When the battery gets old, its chemical reaction slows down and its internal push gets weaker and weaker. Current. Again, everyone uses this term without really knowing what it means. In very simple terms, current is the flow rate of the electrons in the circuit. How is that different from voltage? Let's use a water tank and a pipe as an example.   In some neighborhoods you'll see a water tank raised high above the ground on strong legs. The water in this tank has been raised up there to give it pressure. A series of pipes carry the water down from the tank, under ground, into your house, and then to each sink, bathtub, and toilet. The water in your pipes is under pressure because the water in the tank is pushing down on it. This pressure is similar to Voltage. Voltage is the pressure pushing on the electrons in a circuit.  If all of the faucets in your house are closed, no water flows through the pipes. If you open one faucet, some water flows. If you open all of the faucets, a lot of water flows. This flow of water is similar to electrical Current. Current is the flow rate of electrons through the circuit.

Are Voltage and Current Related? Voltage and current are not the same thing, although they are closely related. In simple terms, Voltage causes Current. Given a Voltage and a path for the electrons, current will flow. Given the path, but no Voltage, or Voltage without the path, there will be no current.