# The property of a magnetic circuit of opposing the passage of magnetic flux lines is called as ______

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The property of a magnetic circuit of opposing the passage of magnetic flux lines is called as ______
1. impedance
2. resistance
3. reluctance

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Correct Answer - Option 3 : reluctance

Concept:

Reluctance opposes the passage of magnetic flux lines. Reluctance is analogous to resistance.

We can define the reluctance as,

$\Re = \frac{{mmf}}{{flux}}$

We know that, $H = \frac{{NI}}{l}$

Where H is field strength

N is the number of turns in a coil

l is mean length of flux in a magnetic circuit

I is current through the coil

The flux in a magnetic circuit is given by

$\phi = BA$

$= \mu HA$

$= \mu \left( {\frac{{NI}}{l}} \right)A$

$\Rightarrow \phi = \frac{{NI}}{{\frac{1}{\mu }\frac{l}{A}}} = \frac{{mmf}}{{reluctance}} = \frac{{mmf}}{\Re}$

Now, we can define reluctance as $\Re = \frac{l}{{\mu A}} = \frac{l}{{{\mu _0}{\mu _r}}A}$

Important Points:

Impedance(Z) is given by Z = R + jX

Where,

Z = Impedance in Ohm

R = Resistance in Ohm

X = Reactance in Ohm

Then Admittance(Y) can be expressed as

Y= a + jb

Where,

a = Conductance in siemens $= \frac{R}{{{R^2} + {X^2}}}$

b = Susceptance in siemens $= \frac{{ - X}}{{{R^2} + {X^2}}}$