MCQ
Two reasons for using soft iron as the material for electromagnets
- ✓high permeability and low retentivity
- Blow permeability and low retentivity
- Clow permeability and low retentivity
- Dlow permeability and high retentivity
✓
Answer
Correct option: A.
high permeability and low retentivity
a
Magnetic retentivity determines the magnetism left in the material after the magnetizing field has been switched off. Electromagnets are operated in conditions requiring fast reversal of polarity, so high retentivity is undesirable. Susceptibility determines to what extent the material responds to the applied field. This means it determines the extent to which the material will be magnetized when a field of given strength is applied. Therefore, electromagnets must be made of materials having high susceptibility and low retentivity. Soft iron is such a material.
Magnetic retentivity determines the magnetism left in the material after the magnetizing field has been switched off. Electromagnets are operated in conditions requiring fast reversal of polarity, so high retentivity is undesirable. Susceptibility determines to what extent the material responds to the applied field. This means it determines the extent to which the material will be magnetized when a field of given strength is applied. Therefore, electromagnets must be made of materials having high susceptibility and low retentivity. Soft iron is such a material.
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