Basic Electrical Theory
MAGNETISM
Magnetic Flux
The group of magnetic field lines emitted outward from the north pole of a magnet is called
magnetic flux. The symbol for magnetic flux is F (phi).
The SI unit of magnetic flux is the weber (Wb). One weber is equal to 1 x 108 magnetic field
lines.
Example:
If a magnetic flux (F) has 5,000 lines, find the number of webers.
F
5000 lines
1 x 108 lines/Wb
5 x 103
108
50 x 106 Wb
50 µWb
Magnetic Flux Density
Magnetic flux density is the amount of magnetic flux per unit area of a section, perpendicular to
the direction of flux. Equation (1-11) is the mathematical representation of magnetic flux
density.
(1-11)
B
F
A
where
B
=
magnetic flux density in teslas (T)
F
=
magnetic flux in webers (Wb)
A
=
area in square meters (m2)
The result is that the SI unit for flux density is webers per square meter
. One weber per
Wb
m2
square meter equals one tesla.
Rev. 0
Page 29
ES-01