The tesla (T) is the SI derived unit of magnetic field B, also known as “magnetic flux density” or “magnetic induction”. The definition is that 1 Tesla (T) is the strength of a magnetic field that would generate a force of 1 newton (N) on a particle carrying a charge of 1 coulomb (C) and travelling at 1 metre per second (m/s).
A typical house magnet, such as a fridge magnet, has a strength in the order of milliteslas. A loudspeaker magnet would be measured in Teslas. At a more extreme end of the scale, the magnetic field of the earth is measured in microteslas, whereas a neutron star would be in the megateslas.
The Tesla was named after Nikola Tesla (1856-1943) who was born in what is now Croatia.
After arriving in the United States in 1884, he worked for Thomas Edison for a couple of years. After falling out over money, Tesla went on to set up his own company which rivaled the Edison company.
He developed methods for the generation and transmission of AC Power, partnering with George Westinghouse to develop this into a commercial business. In what became known as the war of the currents Tesla’s AC system contested Edison’s already established DC system. The AC system, with its many practical advantages, became the adopted standard worldwide.
Other inventions attributed to Tesla include induction (AC) motors and the Tesla coil.