Class 12 Physics Chapter 5 Magnetism and Matter – Revision Notes

Quick revision notes for Class 12 Physics Chapter 5 (Magnetism and Matter). These Class 12 Physics Chapter 5 notes are ideal for quick revision just before exams.

Bar Magnet

• Magnetic moment: m=q_m×2l.
• Axial field: B=(μ₀/4π)(2m/r³); Equatorial: B=(μ₀/4π)(m/r³).
• Torque τ=mB sinθ; PE U=−mB cosθ.

Earth’s Magnetism

• Declination, dip/inclination, horizontal component B_H=B cos(dip).

Material Classification

• Diamagnetic: χ<0, weakly repelled (e.g. bismuth).
• Paramagnetic: χ>0 small, weakly attracted (e.g. aluminium); Curie’s law χ∝1/T.
• Ferromagnetic: large χ>0, strongly attracted, hysteresis (e.g. iron).

One-Line Summary

A bar magnet behaves as an equivalent solenoid producing dipole-like fields; materials are classified as diamagnetic, paramagnetic, or ferromagnetic based on their magnetic susceptibility.

Written by Satish

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