Question

A paramagnetic material is kept in a magnetic field. The field is increased till the magnetization becomes constant. If the temperature is now decreased, the magnetization:

• A. Will increase
• B. Will decrease
• C. Remains constant
• D. May increase or decrease

Hint:

Constant magnetization means saturation; all dipoles are already aligned, so cooling changes nothing.

Answer 1

The Correct Option is C

Reasoning: The clue is that the magnetization was driven until it stopped changing with field. That is the saturation state, in which the fraction of aligned dipoles is already $100\%$.

Effect of cooling: Temperature affects a paramagnet only by opposing alignment through thermal randomization. Cooling helps alignment, but here alignment is already complete. The upper limit of magnetization is set purely by geometry and dipole strength, $M_s = n m$, both temperature independent quantities. Therefore reducing $T$ cannot push $M$ any higher, nor lower it.

Hence the magnetization stays at its saturated value.
\[\boxed{\text{No change; magnetization stays constant}}\]