R is called the reluctance of the magnetic. Equation (1.10)
suggests that the driving force in the magnetic circuit of Fig.1.2
is the magnetomotive force mmf, which produces a flux φ
against a magnetic reluctance . The magnetic circuit of the
toroid can therefore be represented by a magnetic equivalent
circuit as shown in Fig.1.3. Also note that Equation (1.10) has
the form of Ohm's law for an electric circuit (i = E/R). The
analogous electrical circuit is shown in Fig.1.3. A magnetic
circuit is often looked upon as analogous to an electric circuit.
The analogy is illustrated in Table 1.1.
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Magnetic circuit equivalent and electric circuit analogy for the
electromagnet circuit
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Magnetic circuit equivalent and electric circuit analogy for the
electromagnet circuit
If the reluctance of core and air gap is written as
The above magnetic circuit with an air gap can be represented in
a magnetic circuit diagram as shown in figure 4.15(a) and it is
analogous to a series electric circuit in figure 4.15(b). Further if
HcLc and HgLg are regarded as the m.m.f. drops (analogy to voltage
drops in electric circuit) across the reluctance of the core and air
gap respectively, Eq. (4.32) derived from Ampère’s circuital law can
be interpreted as an analogue to the Kirchhoff’s voltage law (KVL)
in electric circuit theory,
a magnetic circuit diagram as shown in figure 4.15(a) and it is
analogous to a series electric circuit in figure 4.15(b). Further if
HcLc and HgLg are regarded as the m.m.f. drops (analogy to voltage
drops in electric circuit) across the reluctance of the core and air
gap respectively, Eq. (4.32) derived from Ampère’s circuital law can
be interpreted as an analogue to the Kirchhoff’s voltage law (KVL)
in electric circuit theory,
Eq. (4.33) states that the algebraic sum of the rises and drops of
the magnetomotive force around a closed loop of a magnetic
circuit is equal to zero. In other words, the sum of the magnetomotive
force rises equals the sum of the magnetomotive drops around
a closed loop.
the magnetomotive force around a closed loop of a magnetic
circuit is equal to zero. In other words, the sum of the magnetomotive
force rises equals the sum of the magnetomotive drops around
a closed loop.
If c and g are regarded as the “current entering/leaving”
a junction in the magnetic circuit, Eq. (4.29a) derived Gauss’s
law of magnetism can be interpreted as an analogue to
the Kirchhoff’s current law (KCL) in electric circuit theory,
a junction in the magnetic circuit, Eq. (4.29a) derived Gauss’s
law of magnetism can be interpreted as an analogue to
the Kirchhoff’s current law (KCL) in electric circuit theory,
Eq. (4.34) states that the algebraic sum of the fluxes entering or
leaving a junction of a\ magnetic circuit is equal to zero. In other
words, the sum of the fluxes entering a junction is equal to the sum
of the fluxes leaving a junction.
The differences between electric and magnetic circuits
-The path of the magnetic flux flows is perpendicular to the current
flows in the circuit. In other words, the directions of B and J are
perpendicular.
-For a given temperature, electric resistance is constant and does
not depend on current density. However, the magnetic reluctance
depends on magnetic field and flux intensity since the permeability
is not constant.
-Current flowing in a electric circuit involves dissipation of energy,
but for magnetic circuit, energy is needed to generate magnetic flux.
Some corresponding quantities in electric and magnetic circuit are
listed as below.
leaving a junction of a\ magnetic circuit is equal to zero. In other
words, the sum of the fluxes entering a junction is equal to the sum
of the fluxes leaving a junction.
The differences between electric and magnetic circuits
-The path of the magnetic flux flows is perpendicular to the current
flows in the circuit. In other words, the directions of B and J are
perpendicular.
-For a given temperature, electric resistance is constant and does
not depend on current density. However, the magnetic reluctance
depends on magnetic field and flux intensity since the permeability
is not constant.
-Current flowing in a electric circuit involves dissipation of energy,
but for magnetic circuit, energy is needed to generate magnetic flux.
Some corresponding quantities in electric and magnetic circuit are
listed as below.
