Paramagnetic Substances – Magnetism & Matters | Class 12 Physics Notes

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Paramagnetic substances

The substances which when placed in a magnetic field are feebly magnetised in the direction of magnetising field are called paramagnetic substances.

(1) The property of paramagnetism is found to exist in substances whose atoms or molecules have an excess of electron spinning in same direction.

(2) Atoms of paramagnetic substances possess a permanent magnetic dipole moment and thus behave like small bar magnets called atomic magnets.

(3) In absence of external magnetic field paramagnetic substances to not show any magnetism because atomic magnets are randomly oriented so net magnetic dipole moment is zero.

(4) In presence of external field each atomic magnet experiences a torque which tries to rotate and align them parallel to direction of magnetic field. The substance acquires net dipole moment and thus gets magnetised in direction of field.

(5) The property of paramagnetism is temperature dependent. The thermal agitation on increase of temperature spoils the alignment of atomic magnets which reduces net magnetic dipole moment.

1. Some paramagnetic substances are $A \ell, N a,$ Sb, Pt, $\operatorname{CuC} \ell_{2}, M n,$ Cr, liquid oxygen etc.