The property of a material which opposes the creation of magnetic flux in it is known as

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Examoogle · Accepted Answer

Reluctance

Explanation: Reluctance is defined as the measure of the opposition a material offers to the establishment of magnetic flux within a magnetic circuit. It is analogous to electrical resistance in an electric circuit, where resistance opposes the flow of current.

Working Principle: When a magnetomotive force (MMF) is applied to a magnetic material, it attempts to drive a magnetic flux through the core. The material's atomic structure and magnetic properties determine how easily flux lines can align; reluctance acts as the inherent 'magnetic resistance' that restricts this alignment, determined by the material's geometry and permeability.

Key Formulas: $S = \frac{l}{\mu A}$ — Formula for reluctance; $S = \frac{MMF}{\Phi}$ — Definition based on Ohm's law for magnetic circuits

Key Points: Reluctance is the reciprocal of permeance.; The unit of reluctance is Ampere-turn per Weber ($At/Wb$).; High permeability materials (like iron) exhibit low reluctance, allowing higher flux for the same MMF.; Reluctance depends on the length, area, and magnetic permeability of the material.

Advantages: Useful for calculating magnetic flux density in transformers and motors.; Provides a simplified way to model complex electromagnetic systems.

Disadvantages: Reluctance is non-linear in ferromagnetic materials due to saturation effects.; Depends on permeability which varies with temperature and flux density.

Applications: Design of electromagnetic actuators and solenoids.; Analysis of transformer cores and electrical machine magnetic paths.

Additional Info: Permeance (Option A) is the reciprocal of reluctance ($1/S$), representing ease of flux creation.. Magnetomotive force (Option C) is the cause of flux, similar to EMF in electrical circuits.. Reluctivity (Option D) is the magnetic counterpart of resistivity, defined as $1/\mu$.

Answer: B is correct — Reluctance is the property of a magnetic material that opposes the formation of magnetic flux within itself.

Exam Tip: Always remember the analogy: MMF $\approx$ Voltage, Flux $\approx$ Current, and Reluctance $\approx$ Resistance to solve magnetic circuit problems quickly.

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