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Explain Curie's law. |
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Answer» SOLUTION :Experimentally it was found that the magnetisation of a PARAMAGNETIC material is inversely proportional to the absolute temperature T. Curie experienced that magnetization of paramagnetic substance is directly proportional to external magnetic FIELD `B_0` and inversely proportional to absolute room temperature. `therefore M= C(B_0)/( T) ""...(1) and M= chi H ""...(2)` and `B_0 = mu_0 H` `therefore M= (Cmu_0 H)/(T)` `therefore (M)/( H) = (C mu_0 )/( T)` `therefore chi = (Cmu_0)/( T) `[From equation (2) ] This is KNOWN as Curie.s law. The constant C is called Curie.s constant. For a paramagnetic material both `chi and mu_r` depend not only on the material but also on the absolute temperature. As the field `(B_0)` is increased or the temperature is lowered the magnetisation increases until it reaches the saturation value `M_S` at which point all the dipoles are perfectly ALIGNED with the field. Beyond this, Curie.s law is no longer valid. |
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