This document defines key terms related to magnetic circuits: 1) A magnetic circuit is a closed path followed by magnetic lines of force. 2) Magnetomotive force (MMF) is the force responsible for generating or flowing magnetic flux, and is measured in ampere-turns. 3) Reluctance is the opposition to the flow of magnetic flux in a material, and is proportional to the length of the magnetic circuit divided by its cross-sectional area.

1. Magnetic
circuit
By
G R chaure

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