Explain the effect of temperature on the magnetic properties of diamagnetic, paramagnetic and ferromagnetic substances.
How to lay out the answer. Follow the frame, then write it in your own words.
1 · State the idea. Thermal agitation upsets the alignment of atomic magnetic moments.
2 · Paramagnets. Heating scatters the permanent moments, so M and χ fall as T rises; cooling raises them, up to saturation.
3 · Ferromagnets. Heating gradually weakens the alignment in the domains; at a high enough temperature the domains break up and the material becomes paramagnetic.
4 · Diamagnets. Induced moments do not depend on alignment, so χ is almost independent of temperature.
5 · Sketch. [Two boxes of domains: arrows lined up within each domain when cool; arrows pointing every way when strongly heated]
6 · Real life. Rice cookers switch off when a magnetic part in the base gets hot enough to lose its strong magnetism.
7 · Close in one line. So, heating weakens para- and ferromagnetism but leaves diamagnetism almost unchanged.
Scoring tip: Cover all three types. Many answers skip diamagnets, and that line carries a mark.
