Question

By giving the examples, explain the meaning of diamagnetic and paramagnetic materials.

Hint:

Diamagnetic substances are weakly repelled (\( \mu_r < 1 \), e.g. bismuth, copper); paramagnetic substances are weakly attracted (\( \mu_r > 1 \), e.g. aluminium, platinum).

Answer 1

Step 1 (Diamagnetic materials): These are substances that are feebly repelled by a magnetic field and tend to move from a stronger to a weaker part of the field. Their atoms have no permanent magnetic moment (paired electron spins), so a weak moment is induced opposite to the applied field. Their relative permeability is slightly less than 1 \( (\mu_r < 1) \) and susceptibility is small and negative.
Examples: bismuth, copper, water, gold, silver.
Step 2 (Paramagnetic materials): These are substances that are feebly attracted by a magnetic field and tend to move from a weaker to a stronger part of the field. Their atoms have a permanent magnetic moment, which partially aligns along the applied field. Their relative permeability is slightly greater than 1 \( (\mu_r > 1) \) and susceptibility is small and positive.
Examples: aluminium, platinum, oxygen, sodium, manganese.
\[\boxed{\text{Diamagnetic: repelled, } \mu_r<1;\quad \text{Paramagnetic: attracted, } \mu_r>1}\]