Electric Cells

In this text we shall consider electric cells. Electrodes being of different materials, a cell supplies electric energy. In case the electrodes are of the same material they become charged but there is no difference of potential across the terminals¹. Iron and zinc plates are commonly used for producing negative electrodes since these materials produce a high charge. Carbon is commonly used to produce positive electrodes. The voltage output² of cells is from 1 to 2V. The value of the output depends only on the materials used for the electrodes. Besides, it depends on the electrolyte of a cell. It does not depend on the size of a cell and its construction, while the current capacity³ of a cell depends on the size of the electrodes. The larger the size of the electrodes, the more current capacity which they can supply. The size of the electrodes beingincreased, the current capacity also increases, the voltage outputremaining the same. Such is the relation between the size of the electrodes and the current capacity.

Пояснения к тексту

Across the terminals— на клеммах

The output — на выходе

The current capacity — пропускная способность

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Electronic Computing Machines

Before describing electronic machines it is useful to con­sider computing machines in general. There are two main classes of computing equipment known respectively as analogue and digital machines. In analogue machines numbers are represen­ted by physical quantities such as the angular rotation of a shaft or the current in a resistor, the numbers being the measu­res¹ of those physical quantities. Examples of analogue machi­nes are the planimeter, the differential analyser, resistance network², etc.

Because they are dependent on the accuracy of physical measurements, analogue machines are strictly limited in regard to the precision of which they are capable. Even with a well designed planimeter, for example, it is difficult to calculate areas to more than four significant figures. For most physical problems this does not constitute a severe restriction and a far more serious limitation of analogue machines is that they are, in general, special purpose devices.

It is known that digital machines, on the other hand, work directly with numbers in digital form and are capable of perform­ing exactly the fundamental operations of arithmetic, addition and subtraction, and usually also multiplication and division.