MAGNETIC UNITS CONVERSION
DEFINITIONS, ONLINE CALCULATORS, EQUATIONS IN SI AND CGS
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Magnetic field
is one of two components of the electromagnetic field. It refers to a region where forces acting on moving electric charges can be detected. Magnetic fields are created by moving electric charges or variable electric field. The charge movement that creates the field may be macroscopic (currents in conductors), or microscopic (associated with spin and orbital motion of electrons, resulting in so-called "magnetic materials").The SI unit for magnetic flux is the weber (Wb). If this flux changes by 1 Wb over a time of 1s, then a voltage of 1 V is induced in a conductive loop encircling it: 1 Wb = 1 Vs.
The flux density is called induction. The SI magnetic induction unit B is tesla (T): 1 T = 1 Wb/m2 = 1 Vs/m2. Magnetic field with density of 1 T generates one newton of force per ampere of current per meter of conductor.
When the fields generated by currents pass through some materials they can produce magnetization in the direction of the applied field. In ferromagnetics it results in increased total field B. Quantity called magnetic field strength (magnetizing force) H is a measure of the applied magnetic field from external currents, independent of the material's response. CGS unit of magnetic field strength is oersted, and SI unit is ampere/meter. Magnetisation M defines the material's response- it is magnetic moment per unit volume of material. Flux density (magnetic induction) B describes the resulting field in the material, which is a combination of an applied field and the magnetization. In power electronics it is the main quantity used in calculation of the required cross-sectional area of power transformer cores for given voltage and frequency (see also: engineering reference info on power transformer design).
The table below provides the magnetism formulas in both SI and CGS systems and conversion factors for the magnetic units.
MAGNETIC FLUX DENSITY UNIT
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 |
MAGNETIC FIELD STRENGTH UNIT
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| QUANTITY | SYMBOL | SI UNIT | SI EQUATION | CGS UNIT | CGS EQUATION | CONVERSION FACTOR |
| Magnetic induction |
B | tesla (T) | B=µo(H+M) | gauss (G) | B = H+4πM | 1 T = 104 G |
| Magnetic field strength | H | ampere/meter (A/m) |
H
= N×I/lc ( lc - magnetic path, m) |
oersted (Oe) | H
= 0.4πN×I/lc (lc - magnetic path, cm) |
1
A/m = 4 π×10-3 Oe |
| Magnetic flux | Φ | weber (Wb) | Φ
=
B×Ac (Ac - area, m2 ) |
maxwell (M) | Φ
=
B×Ac (Ac - area, cm2 ) |
1 Wb = 108 M |
| Magnetization | M | ampere/meter (A/m) | M=m/V (m- total magnetic moment, V- volume, m3 ) |
emu/cm3 | M=m/V (m- total magnetic moment, V- volume, cm3 ) |
1
A/m = 10-3 emu / cm3 |
| Magnetic
permeability of vacuum |
µo | newton/ampere2 |
µo= 4π×10-7 | 1 | - | 4π×10-7 |
| Inductance | L | henry | L=μoμN2Ac/lc (Ac- area, m2, lc - magnetic path, m) |
henry | L=0.4πμN2Ac/lc×10-8 (Ac-area, cm2, lc - magnetic path, cm) |
1 |
| Emf (voltage) | V | volt | V=-N×dΦ/dt |
volt | V=-10-8N×dΦ/dt |
1 |
| Note: in the above equations: N- turns, I - current (in amps) | ||||||
