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Magnetic Properties of Matter question

2004 · Shift 0 · Q146
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Magnetic Properties of Matter question

2004 · Shift 0 · Q146

JEE MainPhysicsMagnetic Properties of MatterMCQ+4 / −1
The materials suitable for making electromagnets should have
  1. A
    high retentivity and low coercivity
  2. B
    low retentivity and low coercivity
  3. C
    high retentivity and high coercivity
  4. D
    low retentivity and high coercivity
View written solutionFree

Correct answer: B

  1. Relevant magnetic properties

    For a good electromagnet, the material should:

    • get magnetized strongly and easily when current flows,
    • lose its magnetism quickly when current is switched off.

  2. Meaning of the terms

    • Retentivity: ability of a material to retain magnetization after the magnetizing field is removed.
    • Coercivity: reverse magnetic field required to demagnetize the material.

  3. Requirement for electromagnets

    Since an electromagnet should not remain magnetized strongly after current is turned off,

    • it should have low retentivity.

    Also, it should be easy to magnetize and demagnetize,

    • so it should have low coercivity.

  4. Checking the options

    • A: high retentivity and low coercivity →\rightarrow→ retains magnetism too much, not suitable.
    • B: low retentivity and low coercivity →\rightarrow→ suitable.
    • C: high retentivity and high coercivity →\rightarrow→ suitable for permanent magnets, not electromagnets.
    • D: low retentivity and high coercivity →\rightarrow→ difficult to demagnetize, not suitable.

  5. Final answer

    The correct option is: B\boxed{\text{B}}B​

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