A pocket electric station

By using radioactive isotopes it is possible to obtain electric energy from the energy of radioactive radiation directly. Very small atomic electric batteries have already been constructed and they have certain advantages over common electric batteries.

Among the different substances in nature, there is a big group of so-called semiconductors, which occupy a position between conductors of electric current and non-conductors. These "half" conductors conduct electric current, but do it much worse than metals.

It wasn’t so long ago that these substances were like a hidden treasure in the earth, with their properties hardly known. However, science having made considerable progress during the past years has greatly changed our ideas about these substances. Semiconductors have appeared in modern technology, forming a new and very important field of science, the physics of semiconductors.

It was found that current flow in semiconductors is entirely different from that in metal conductors. When a metal wire carries current, this means that the so-called free electrons are moving within the wire in a given direction. Such free electrons are always present in metals. Not so with semiconductors.

Depending upon certain conditions, there may or there may not be free electrons in them. For example, at low temperature there are hardly any free electrons at all, and the semiconductor does not conduct electric current. But heating such a substance causes to appear and the semiconductor begins conducting electricity. Semiconductors may be acted upon in the same way by light and radioactive radiation. It is the property that is used in atomic electric batteries.

The fast electrons from the radioactive substance displace large numbers of new electrons in the semiconductor, producing a flow of electrons in one direction, or in other worlds, an electric current. True, this current is very small. But atomic batteries will produce a current strong enough for radio sets, telephones and the like. Atomic batteries can operate a very long time without being charged again.

COMMENTARY

conduct electric current – здійснюють електричний струм

in a given direction – у даному напрямку

free electrons – вільні електрони

atomic batteries – атомні батареї

without being charged again – без підзарядки

electric current – електричний струм

does not conduct – не проводить

in a given direction – в даному напрямку

occupy a position – займає позицію

Principles of modern radar

Modern radar has advanced far beyond the have equipment of short range and limited accuracy that appeared as one of the major technical achievements after World War II.

Through continuous improvement it has been possible to increase distances. Accuracy having been infinitely improved through increased use of microwaves and the development of electron tubes capable of handling such wavelengths; the usefulness of radar has been considerably expanded.

Radar has many peaceful uses. To help navigation at sea, small radars are installed on small commercial vessels, and larger setups are used on ocean-going liners and transports.

Aboard aircraft is used to make air navigation and flight safe, and to map areas over which the plane is flying. Ground-based radar is employed to control flights of aircraft.

In detecting storms, radar can locate heavy clouds associated with various weather disturbances.

Whatever the application, the basic principles of all types of radar equipment are deeply rooted in radio and electronics.