At the microscopic level, many molecules are magnets - hydrogen fluoride for example is a dipole. In most substances, all of the magnetic fields produced by this motion cancel each other out, but magnetic substances have more proper alignment. It is derived from basic standard units, but is expressed directly in base units and cannot be further reduced. In fact, all substances have charges moving in them all of the time, one of the difficulties in reaching absolute zero. ampere per meter (A/m, Oe, oersted): The ampere per meter (symbolized A/m) is the International Unit of magnetic field strength. The idea that magnetic forces act on moving charges is clear in an electromagnet but not obvious in a permanent magnet. A vector pointing along an axis becomes one-dimensional, or identical to a scalar. In fact, charge is a vector whose direction is determined by the spin of a particle, but macroscopic calculations are not concerned with this direction and define charge to be along an axis so that the direction of another vector is really its direction relative to charge. However, the strength of a magnetic field is measured in teslas and one tesla is one newton per ampere-metre which confirms that the unit for pole strength is indeed the ampere-metre.Ĭharge is usually thought of as a scalar or a quantum number while velocity is a vector. Magnets are dipoles which require more complicated calculations than monopoles. Therefore, the pole strength is the product of charge and velocity.įew calculations actually involve the strength of a pole in ampere-metres because a single magnetic pole has never been isolated. This means that while an electric field acts between charges, a magnetic field acts between moving charges (as a charge moves through space more quickly and through time more slowly, its electromagnetic force becomes more magnetic and less electric). In fact, charge is a vector whose direction is determined.
Charge is usually thought of as a scalar or a quantum number while velocity is a vector. Einstein proved that a magnetic field is the relativistic part of an electric field. However, the strength of a magnetic field is measured in teslas and one tesla is one newton per ampere-metre which confirms that the unit for pole strength is indeed the ampere-metre.