Ex 2. Find Russian equivalents for the English ones.

1. charged particles	1. крошечный дисбаланс
2. practical level	2. древние исследователи
3. electron excess	3. заряженные частицы
4. tiny imbalance	4. поведение внутренней структуры
5. positive and negative charges	5. избыток электронов
6. current flow	6. электрический заряд
7. electrical phenomena	7. практический уровень
8. electric charge	8. положит. и отрицат. заряды
9. bulk behavior	9. поток тока
10. early researches	10. электрическое явление

Ex 3. Translate from Russian into English.

1. Фактически, простое электрическое явление возникает из-за невероятно крошечной разницы между количеством положительно заряженных протонов и отрицательно заряженных электронов. 2. Лейденские банки были кувшинами, снаружи и внутри отделанные металлической фольгой. 3. Электрический заряд может быть как положительным, так и отрицательным. 4. Единицей тока является ампер, обозначающийся как «А». 5. Лейденские банки были ни чем иным как конденсаторами, а их стекло служило диэлектриком. 6. Существует огромное количество электрических единиц и большое количество учёных, в честь которых они названы. 7. То, что мы называем током является потоком положительного заряда в одном направлении или отрицательного заряда в другом. 8. С точки зрения атомной физики, электричество – одно из фундаментальных сил природы.

Ex 4. Make up the outline of the text. Retell the text using your outline.

Ex 5. Complete the following sentences.

1. Electricity describes the phenomena associated with … 2. The imbalance between photons and electrons … 3. … is caused by electrons moving away from the atomic nuclei to which they belong. 4. … which were glass jars with metal foil on the inside and outside. 5. We now know that the jars were just capacitors with … 6. … electric charge can be either positive or negative. 7. Current flow is always considered to be … 8. … abbreviated “C”, and named after Charles Augustin Coulomb. 9. … is perhaps too theoretical for practical use. 10. There are an enormous number of electrical units, and an enormous number of scientists after whom they are named…

Ex 6. Match Russian and English terms in columns A and B.

A: particle, excess, tiny, capacitor, coincidence, charge, current, jar, nuclei, bulk

B: избыток, заряд, совпадение, кувшин (банка), ядро, внутренняя структура, частица, крошечный, ток, конденсатор.

Text 1.2

Energy, Power, and Voltage

 

We are going to use the hydraulic analogy again. It takes energy to pump water uphill, and the potential energy of being at a high elevation is released when it descends to a lower elevation. The amount of energy (in joules) is mgh, where m is the mass of liquid (say, in kilograms), g is the strength of gravity (9.8 meters per second squared, or 9.8 newtons per kilogram), and h is the elevation distance.

Some elementary physics: The SI unit of energy is the joule, and is one newton-meter, and is the energy required to push something with a force of one newton through a distance of one meter. The unit of force is the newton, and is the force required to increase the speed of a one kilogram object by one meter per second per second. The unit of rate of flow of energy is the watt, and is one joule per second. Note that the watt relates to all of physics, not just electricity.

For a given difference in elevation h, it takes gh joules of energy per kilogram to lift water (or any other liquid) through that height. That same amount of energy is released when the water flows down by that height. It might drop directly—old-fashioned water wheels use this method, or the water might be stored in a reservoir, causing the water to have enormous pressure at the bottom. That pressure gives the water a lot of energy per kilogram, which can be recovered by turbines—modern hydroelectric power stations do this. The amount of pressure at the bottom of a column of water of height h is enough to release gh joules per kilogram.

The electrical analogue of this pressure is voltage. The unit is the volt, named after Alessandro Volta. It is the amount of "pressure" that releases one joule per coulomb of charge. A given region of space (or, more commonly in practice, a given point in an electrical circuit) has a certain voltage potential. If two points differ in potential by V volts, then the passage of Q coulombs of charge from one point to the other releases QV joules of energy. This "potential difference" or "voltage difference" is analogous to the difference in height (and hence difference in pressure) between water at the top of a reservoir and water at the bottom.

In fact, some very old books refer to voltage as "electrical pressure". Another term for voltage that one sees in older books is "electro-motive force" or its abbreviation "emf". It's just voltage.

There is another useful analogy to water. The level of water on a pond is uniform, that is, the surface is level. This is because the water can travel very easily from one point to another. If the surface were higher at one point than at another, the water would simply flow from the higher point to the lower one, until equilibrium is reached. Similarly, in a conductor (e.g. a wire), electrons can flow very easily from one point to another, so there is essentially no voltage difference. If there were, the electrons in the wire would simply flow from the higher voltage to the lower voltage (well, actually, they would flow the other way because their charge is negative) until the voltage is equalized. Hence, all points in an electric circuit that are connected by a wire are at the same voltage.

This only applies to situations in which the water or the charges can move easily. In a river, there is some resistance to the motion, so the water is constantly moving from higher elevations to lower elevations. Not all conductors are perfect, so there is actually a slight voltage drop (and dissipation of power) across a conductor. How great this effect is depends on the resistance, in accordance with Ohm's law, which we will discuss presently.