Soft iron for temporary magnets – statement evaluation Is the following statement correct? “Soft iron is suitable for making temporary magnets.”

Electronics and Communication Engineering Materials and Components Difficulty: Easy
Choose an option
  • A
    True
  • B
    False
  • C
    True only at cryogenic temperatures
  • D
    False; hard steel is used instead
  • E
    True only if alloyed with nickel

Answer

Correct Answer: True

Explanation

Introduction / Context:Magnetic materials are broadly chosen as either soft (easily magnetized and demagnetized) or hard (retain magnetization). Understanding this distinction is vital for cores, relays, transformers, and temporary electromagnets.

Given Data / Assumptions:

  • Soft iron has high permeability, low coercivity, and low hysteresis loss.
  • Temporary magnet means it should follow the applied field and lose magnetization when the field is removed.
  • Contrast with hard magnetic materials (e.g., AlNiCo, ferrites) used for permanent magnets.

Concept / Approach:

Soft iron’s low coercive force means small fields can magnetize it strongly and removing the field collapses magnetization. This is ideal for temporary magnets and AC magnetic circuits. Hard magnets require large coercive fields to demagnetize and are not suitable for temporary applications.

Step-by-Step Solution:

Identify requirement: easy magnetization/demagnetization → low coercivity.Soft iron exhibits μ_r ≫ 1 and narrow hysteresis loop → small losses.Conclusion: soft iron is the correct choice for temporary magnets.

Verification / Alternative check:

Transformer laminations, relay cores, and electromagnet yokes are made from soft magnetic steels or irons, confirming the practical preference.

Why Other Options Are Wrong:

(b) contradicts magnetic design practice; (d) confuses permanent vs. temporary needs; (e) alloying can tune properties but is not a prerequisite for the truth of the statement.

Common Pitfalls:

Assuming “strong magnet” always equals “good magnet”; application determines whether soft or hard magnetic behavior is desirable.

Final Answer:

True

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