Tesla as a Unit of Measurement

Tesla as a Unit of Measurement

From the very beginning of the development of modern science, a need to introduce units of measurement for quantitative labeling of natural phenomena appeared.  During the 18th and the 19th century, science and technology were in great rise.  With their accelerated development, the exchange of scientific achievements became greater as well. 

Different scientific associations, however, as well as the scientists themselves, used different units for labeling the same natural quantities.  This lead to problems in the exchange of scientific works, as well as in translating quantities from one unit to another.  There was a constant need, therefore, to coordinate systems of measurement so the development of science could proceed unhampered.

The first step toward the current system of measurement was made on June 22nd 1799 when the decimal metric system was introduced.  Two platinum rods, representing standards for one meter and one kilogram, were then exhibited in the Archive of the Republic (Archives de la République) in Paris.  Many great scientists pointed to the need for further development and the introduction of a unified system of measurement.  As long ago as 1832, Karl Friedrich Gauss (1777-1855) proposed the use of the metric system together with the unit of a second, as a coherent system of units in natural sciences.

In 1860, James Clerk Maxwell (1831-1879) proposed the introduction of a unit system with basic units and derived units.  After that, in 1874, British Association for the Advancement of Science (BAAS) introduced the CGS (centimetre, gram, second) unit system.  The CGS system, however, was not fit for the use in electrical engineering, so in 1880 two more units were introduced – ohm (W) for electrical resistance and volt (V) for electromotive force.  The units received their names after the great scientists Alessandro Giuseppe Volta (1745-1827) and Georg Simon Ohm (1789-1854).

As a result of the Metre Convention, held on May 20th 1875, in 1889 the MKS (metre, kilogram, second) was introduced.  After half a century, in 1939, the base unit for electric current, ampere [A], was added, named after the French scientist André-Marie Ampère (1775-1836).  Thus MKS became MKSA (metre, kilogram, second, ampere) unit system.  The SI system of units (Système International d’Unités) we use today was adopted in 1960 at the 9th General Conference for Weights and Measures, which assembled 34 countries, signers of the Metre Convention.

Tesla’s research changed our lifestyle to an extent we are not aware of.  Looking from the perspective of a highly developed technological society we live in, Tesla’s inventions do not look overly advanced.  Still, Tesla’s inventions are used everyday worldwide in a more or less modified form.  The principle bases of his inventions are part of almost every electrical device. 

During the time Tesla lived and worked, his experiments were bordering science fiction.  Even the most famous and distinguished scientists of the period remained speechless in front of the experiments he performed.  Considering his contributions to electrical engineering, the assigning of his name to the unit of measure is an adequate recognition of his work.

The unit bearing Tesla’s name is the unit for magnetic induction.  Earlier, the unit gaus [G] was used as the unit for magnetic induction.  After the introduction of the SI system it was not used anymore.  The proposal for introducing the unit tesla came from the professors of the Belgrade Faculty of Electrical Engineering, Pavle Miljanic and Aleksandar Damjanovic.  Deliberation lasted from 1950, when it was submitted, until 1960, when it was adopted at the 9th General Conference for Weights and Measures. In order to explain the definition of the tesla unit we have to define the physical phenomenon it quantifies, and that is magnetic induction.  Magnetic induction is defined as the number of magnetic field lines per surface unit.  People have noticed long ago that magnets attract and repulse metal objects without physical contact.  On the basis of this phenomenon, it was concluded that magnets, in a way, have the properties of their environment.  This phenomenon was named magnetic field.

It was agreed to represent magnetic field with lines flowing from the north to the south magnetic pole.  The stronger the magnetic field, the denser the field lines.  The unit for measuring the strength of the magnetic field is Weber [WB].  Magnetic field created by a magnet can best be noticed if small particles of metal are scattered on a flat surface around the magnet, and then vibration of the surface where the magnet is found are made.  The metal particles will be scattered in the direction of magnetic field lines and they will visually manifest the magnetic field of the magnet.  Magnetic induction is defined as the ratio of the number of these lines and the unit of surface through which those lines pass.

Magnetic field, and, consequently, magnetic induction, are present all around us.  We don’t notice them, but even our body produces a weak magnetic field.  It can be observed by using special cameras that register magnetic fields produced by objects.  It is manifested in the form of radiation surrounding our body.  This is our aura.  Planet Earth also possesses magnetic field.  It protects us from harmful influenced coming from space, mainly from ionized particles coming from the sun.

In engineering, 3-4 T of magnetic induction are usually used.  As with gravitational and electric field, the power of magnetic field falls with distance, and, the power of magnetic induction with it.  The intensity range of magnetic induction of natural sources of magnetic field on Earth is great.  Human brain produces magnetic induction of 100.10-15 T.  Magnetic poles of the Earth create magnetic induction a trillion times greater.  The strength range of magnetic induction produced by men during different research varies greatly. The greatest ever magnetic induction on Earth was produced with a controlled explosion in the city of Sarov in Russia.  Magnetic induction of 2800 T was then created.  These strengths of magnetic induction are very small when compared to the strengths of magnetic induction existing in space.  Pulsar creates magnetic induction of 10 billion T, while neutron star creates magnetic induction of 10 trillion T.  The upper potential limit of the strength of magnetic induction is the magnetic induction of neutron star.  The magnetic induction of around 6 T can strip a wristwatch from a distance of four meters.

The recognition a scientist is awarded by having a unit in the unit system named after him is truly great.  Only 15 scientists have received such an honor.  Tesla was placed among such great people as Webber, Herz, Ohm, Volta, Ampere, Kelvin.  Those were grandiose men who fundamentally changed our way of life and our understanding of the universe.