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Electrical quantities

During the reporting period stabilized names of basic electrical quantities, gradually set the terms: electrical resistance, electromotive force, current, amount of electricity, etc .; the use of these terms in the scientific and technical literature is gradually acquiring a definite character.

During the 1830-1860 biennium. many instruments have been built and developed methods for measuring basic electrical quantities. Electrometry solid foundation was laid, but it is still mainly concentrated in the laboratories.

Only since the 70s of the last century is very fast implementation of measurement methods in wide practice. With regard to the units for measuring electrical quantities, during the period under discussion in this area there was unsteady position and many researchers have been entered into a scientific turn their units.

The concept of electrical units while sometimes identified with the standard concept. For example, to measure the electrical resistance of E. Lentz X. (1838) used unit sales as a benchmark, which had the character of a calibrated length of copper wire 1 foot taken from the assortment of the time.

In 1848, Jacobi established the normal standard of resistance, which has been extended in many Russian and European laboratories and had a look and feel that matches our modern ideas of the benchmark.

"Unit Jacobi resistance" was produced in the form of a coil of copper wire 25 feet long, weighing 22.5 grams and a diameter of 0.67 mm and placed in a special box and filled with an insulating compound. The standards of this unit is manufactured serially.

Along with identity Jacobi also existed Siemens unit of resistance, the Wheatstone and others. The confusion in this area looked like at Jacobi expression, the situation in public life, which has developed would be if everyone enjoyed their special meters or pounds.

The need to establish common international units grew more and more; in particular, due to the fact that the Telegraph has turned into an international means of communication, there is a need to unify the resistance units.

The Committee and the absolute electromagnetic system

A big step forward in the establishment of generally accepted units was made in 1861 by the British Association for the Advancement of Science, establish a special committee to develop the question of the standard unit of electrical resistance. The Committee included such prominent scholars as William Thomson (Lord Kelvin), J. Maxwell et al.

The Committee has expanded its program of work and is not limited to the problem of unity and resistance standard, introduced in 1870 by the Association of the project, in which it recommended a system of electrical units, based on the absolute electromagnetic system.

The Committee suggested to the following practical units: Resistance - "OMAD" or "th" e. d. s. - "V", capacitance - "farad". Units power and quantity of electricity was derived from the previous ones, and for their special names were suggested. With regard to the real standard unit of resistance, the Committee stopped on the reference of the wire (alloy of silver and 2 parts 1 part of platinum).

The proposal of the British Association Committee may be only advisory in nature, though mainly for England. The problem acquired great spear, and became absolutely necessary and inevitable consideration of its international scale.

International Congress of electricians 1881

At a 1881 International Congress of electricians discussion of units it became the focus of attention of scientists. Special Commission, established by Congress recognized that electrical units must be based on the metric system, and approved the proposed Committee of the British Association for the basic units: centimeter, gram, second.

Of the two systems - the absolute electrostatic and electromagnetic absolute - absolute recommended for use as an electromagnetic system more convenient for measurement purposes; it does not exclude the possibility of use and absolute electrostatic system.

The Commission has also resolved the issue of the current units and the quantity of electricity, and gave them the name "amps" and "pendant". The final resolution of the issue of units and the reference received at the Chicago Electrotechnical Congress in 1893