ABSTRACT
The pole face is circular, hence area= πr 2, where r is the radius. Hence πr2 = 0.1961
from which r2 = 0.1961 π
and radius r = √(
0.1961 π
)
= 0.250m i.e. the radius of the pole face is 250mm
Magnetomotive force (mmf) is the cause of the existence of a magnetic flux in a magnetic circuit,
mmf,Fm=NI amperes
the current in amperes. The unit of mmf is sometimes expressed as ‘ampere-turns’. However, since ‘turns’ have no dimensions, the SI unit of mmf is the ampere. Magnetic field strength (or magnetizing force),
H= NI/l ampere per metre where l is the mean length of the flux path in metres. Thusmmf=NI= Hl amperes.
