Other Common Systems of Magnetic Units

There are two other systems of magnetic units that are still in use. One of these is the cgs electromagnetic system, which has been used widely in scientific work for a number of years. In addition, there is the Mixed English System of Units, which has also been used for many years and is still used to a considerable extent in this country.

In the cgs system, the unit of flux density is the gauss or one maxwell per square centimeter. One maxwell is 10^-8 weber. In the same system, the unit of magnetic field intensity is the oersted, which is 4π/10 amp turns per cm. This choice of units results in a value of permeability for free space of unity. The unit of magnetomotive force is the gilbert and is equal to 0.4πNI.

In the Mixed English System the unit of flux density is the maxwell per square inch and the unit of magnetic field intensity is the ampere turn per inch.

Actually the rationalized MKS system of units is one that has been accepted, though not universally, only in recent years.

Conversion factors are given in Table 3-2.

TABLE 3-2
Multiply	by	to obtain
F in ampere turns	0.47π	F in gilberts
H in ampere turns/inch	0.47π/2.54	H in oersteds
B in lines/square inch	10-4/6.45	B in webers/square meter
B in lines/square inch	1/6.45	B in gausses

Note:

1 pragilbert = 1,000 gilberts 1 praoersted = 1,000 oersteds