What is the formula of the permeance of the strip in the conductor portion?

Question

Examoogle · Accepted Answer

Option C: permeance of the strip = permeability in air * area of the flux path / length of flux path

Explanation & Concepts:
Permeance is the reciprocal of reluctance in a magnetic circuit, quantifying the ease with which magnetic flux is established in a material. It is defined as the ratio of magnetic flux to magnetomotive force, analogous to conductance in an electric circuit.

Working Principle: In a magnetic strip of uniform cross-section, the reluctance $S$ is given by $S = \frac{l}{\mu A}$. Since permeance $P$ is defined as the inverse of reluctance ($P = \frac{1}{S}$), substituting the reluctance formula yields $P = \frac{\mu A}{l}$, where $\mu$ is permeability, $A$ is the area, and $l$ is the length of the flux path.

Key Formulas: $P = \frac{\mu A}{l}$ — Formula for magnetic permeance; $S = \frac{l}{\mu A}$ — Formula for magnetic reluctance

Key Points: Permeance is the magnetic equivalent of electrical conductance ($G = \sigma \frac{A}{l}$); The SI unit for permeance is Henry (H) or Webers per Ampere-turn (Wb/At); Permeance increases with higher permeability and larger cross-sectional area; Permeance decreases as the length of the magnetic path increases

Advantages: Simplifies calculation of magnetic flux in series and parallel magnetic circuits; Provides a direct measure of magnetic field efficiency in machine design

Disadvantages: Assumes constant permeability, which is inaccurate for ferromagnetic materials due to saturation; Does not account for magnetic leakage flux in complex geometries

Applications: Design of electromagnetic actuators and solenoids; Analysis of transformer cores and electrical motor stators; Calculation of magnetic circuit impedance

Additional Info: The formula reflects that magnetic flux follows the path of least resistance (reluctance).. Option A suggests a product of all parameters, which is dimensionally inconsistent. Option B is the inverse formula (reluctance). Option D is physically incorrect.

Answer: C is correct — Permeance is given by the product of absolute permeability and area divided by the length of the magnetic path.

Exam Tip: Remember that magnetic reluctance $S$ is analogous to electrical resistance $R = \frac{\rho l}{A}$. Always verify dimensional consistency: permeance must have the units of Inductance (Henries).

Examoogle · Answer

Option A: permeance of the strip = permeability in air * area of the flux path * length of flux path

Examoogle · Answer

Option B: permeance of the strip = permeability in air / area of the flux path * length of flux path

Examoogle · Answer

Option D: permeance of the strip =1 / permeability in air * area of the flux path * length of flux path

Correct Answer

Discussion (0)

Correct Answer

Related Questions

Discussion (0)