Assertion (A): The properties of paramagnetic and ferromagnetic substances are not affected by heating.
Reason (R): As temperature changes, the alignment of molecular magnets does not change.
1. (1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. (2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (3) (A) is true but (R) is false
4. (4) Both (A) and (R) are false
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The magnetic properties of paramagnetic and ferromagnetic substances are strongly affected by temperature. Paramagnetic susceptibility is temperature-dependent (Curie's Law), and ferromagnets become paramagnets above their Curie temperature. Thermal agitation due to heating disorients molecular magnets. Both Assertion (A) and Reason (R) are false.
Assertion (A): Soft iron is used as transformer core.
Reason (R): Soft iron has narrow hysteresis loop.
1. (1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. (2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (3) (A) is true but (R) is false
4. (4) Both (A) and (R) are false
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Soft iron is preferred for transformer cores because its narrow hysteresis loop indicates low energy loss (heat) during repeated cycles of magnetisation and demagnetisation. This property is crucial for efficient transformer operation. Both Assertion and Reason are true, and Reason is the correct explanation of the Assertion.