2. Important definition related to magnetic circuit
Magnetic circuit : A closed path fallowed by
magnetic line of force i.e
Magnetic circuit
3. Magneto motive force : the force responsible
for the generation of flux or flow of flux
The magnetic field strength is decided by mmf
MMF is denoted by F and measured in
ampere turns
MMF = N * I
N= no of turns of magnetising coil
I = current in ampere
4. Reluctance :it is defined as the opposition to
flow of flux in a material
It is denoted by S
S= K l/a
K= constant of proportionality
l = length of magnetic circuit in meter
a = area of cross section in 𝑚2
S = mmf / flux = N*I / Ø =
𝐴𝑇
𝑤𝑏
Permeance : reciprocal of reluctance
Magnetic circuit
5. Comparison between magnetic and electric circuit
Electric circuit Magnetic circuit
Current : flow of electrons
through conductor and measured
in ampere
Flux : lines of force through a
medium from N pole to S pole
and measured in weber
EMF is driving force MMF is driving force
Resistance opposition to flow
current in conductor & measured
in ohm
Reluctance is opposition to flow
of flux & measured in AT /wb
Resistance is directly proportional
to length of conductor
Reluctance is directly
proportional to length of
magnetic path
I =
𝐸𝑀𝐹
𝑅𝑒𝑠𝑖𝑠𝑡𝑎𝑛𝑐𝑒
Flux =
𝑀𝑀𝐹
𝑅𝑒𝑙𝑢𝑐𝑡𝑎𝑛𝑐𝑒
Conductance =1/resistance Permeance =1/reluctance
Magnetic circuit
