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Difficulty: HardMagnetism Fundamentals

A technician needs to protect a sensitive electronic component from stray external DC magnetic fields by placing it inside a soft iron enclosure. How does this magnetic shield prevent external magnetic flux from reaching the component?

  1. A
    The enclosure acts as a magnetic insulator, stopping and absorbing magnetic flux before it penetrates the surface.
  2. The enclosure provides a low-reluctance path with high permeability, channeling the flux lines through its walls and around the interior.Answer
  3. C
    The enclosure develops opposing magnetic poles that repel external magnetic field lines away from both sides of the casing.
  4. D
    The enclosure converts incoming magnetic lines of force into an electrostatic charge that is dissipated as heat.

Answer

The enclosure provides a low-reluctance path with high permeability, channeling the flux lines through its walls and around the interior.
Magnetic shielding relies on high permeability and low reluctance. Because there is no known insulator that blocks magnetic flux lines, the soft iron shield provides an easy path of low reluctance that channels the magnetic field lines through its walls, directing them safely around the internal cavity where the sensitive component is placed.

Step-by-Step Solution

1
Identify the magnetic characteristics of the shielding material.
Soft iron is a ferromagnetic substance characterized by high magnetic permeability and low magnetic reluctance.
Permeability describes how readily a material conducts magnetic flux compared to surrounding air, while reluctance represents opposition to flux lines.
2
Determine the path magnetic flux lines follow when encountering the enclosure.
Magnetic flux lines naturally follow the path of least resistance (lowest reluctance), concentrating within the thick iron walls.
Flux lines take the easiest path available rather than crossing the higher-reluctance air gap in the center.
3
Conclude how the interior component is protected.
Because flux lines are guided through the perimeter walls and exit on the opposite side, the internal cavity remains essentially free of magnetic field lines.
Since true magnetic insulators do not exist, diversion through high-permeability conduits is the fundamental method of magnetic shielding.

Key Concept

Magnetic Shielding, Permeability, and Reluctance
Estimated Time:1m 0s
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Topics

Magnetism Fundamentals

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