The International System unit of field intensity for magnetic fields is Tesla (T). One tesla (1 T) is defined as the field intensity generating one newton (N) of force per ampere (A) of current per meter of conductor: T = N × A-1 × m-1 = kg × s-2 × A-1 Certain other non-SI units, like Gauss (G), are still occasionally used. A magnetic field of one tesla is quite strong. That is why magnetic fields are usually expressed in microtesla (µT). Typical values of field intensity for some magnetic fields are: S Field µT Strongest fields available in laboratories 20 000 000 Earth's magnetic field intensity, at its surface 50 Domestic electrical appliances 0.02 to 7 Interstellar magnetic field 0.000 000 3