<Ol> <Li> The magnetic induction field B is given in SI units of teslas (T). B is the magnetic field whose time variation produces, by Faraday's Law, circulating electric fields (which the power companies sell). B also produces a deflection force on moving charged particles (as in TV tubes). The tesla is equivalent to the magnetic flux (in webers) per unit area (in meters squared), thus giving B the unit of a flux density . In CGS, the unit of B is the gauss (G). One tesla equals 10 G . </Li> <Li> The magnetic field H is given in SI units of ampere - turns per meter (A-turn / m). The turns appear because when H is produced by a current - carrying wire, its value is proportional to the number of turns of that wire . In CGS, the unit of H is the oersted (Oe). One A-turn / m equals 4π × 10 Oe . </Li> <Li> The magnetization M is given in SI units of amperes per meter (A / m). In CGS, the unit of M is the oersted (Oe). One A / m equals 10 emu / cm . A good permanent magnet can have a magnetization as large as a million amperes per meter . </Li> <Li> In SI units, the relation B = μ (H + M) holds, where μ is the permeability of space, which equals 4π × 10 T m / A . In CGS, it is written as B = H + 4πM . (The pole approach gives μ H in SI units . A μ M term in SI must then supplement this μ H to give the correct field within B, the magnet . It will agree with the field B calculated using Ampèrian currents). </Li> </Ol> <Li> The magnetic induction field B is given in SI units of teslas (T). B is the magnetic field whose time variation produces, by Faraday's Law, circulating electric fields (which the power companies sell). B also produces a deflection force on moving charged particles (as in TV tubes). The tesla is equivalent to the magnetic flux (in webers) per unit area (in meters squared), thus giving B the unit of a flux density . In CGS, the unit of B is the gauss (G). One tesla equals 10 G . </Li> <Li> The magnetic field H is given in SI units of ampere - turns per meter (A-turn / m). The turns appear because when H is produced by a current - carrying wire, its value is proportional to the number of turns of that wire . In CGS, the unit of H is the oersted (Oe). One A-turn / m equals 4π × 10 Oe . </Li> <Li> The magnetization M is given in SI units of amperes per meter (A / m). In CGS, the unit of M is the oersted (Oe). One A / m equals 10 emu / cm . A good permanent magnet can have a magnetization as large as a million amperes per meter . </Li>

When were the first man made magnets made