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Magnetism and Matter

NCERT Class 12 Physics Chapter 5

Magnetism and Matter for Class 12 Physics, JEE and NEET: the bar magnet as a dipole, Gauss’s law for magnetism and dia-, para- and ferromagnetism.

4 topics Updated 8 Nov 2026

For: Class 12, JEE and NEET

In the syllabus: JEE Class 12 syllabus, NEET Class 12 syllabus

With your textbook

NCERT Physics Part I (Class 12), Chapter 5 “Magnetism and Matter”, reprint 2026-27.

Open the official NCERT chapter (PDF, 1.9 MB, ncert.nic.in)

Checked on 19 Oct 2026.

Learn in this order

  1. The bar magnet

    Field lines, the bar magnet as an equivalent solenoid, its field on the axis and equator, and the torque m × B.

    NCERT Sections 5.1–5.2 15 min read 4 solved examples 9 practice questions

  2. Gauss’s law for magnetism

    Statement and formula, zero flux through any closed surface, monopoles, and NCERT Examples 5.3–5.4.

    NCERT Section 5.3 12 min read 4 solved examples 8 practice questions

  3. Magnetisation and magnetic intensity

    M, H, B = μ(H + M), susceptibility χ and relative permeability μr = 1 + χ, with examples.

    NCERT Section 5.4 13 min read 4 solved examples 7 practice questions

  4. Magnetic properties of materials

    χ ranges, examples, superconductors, domains, effect of temperature.

    NCERT Section 5.5 15 min read 4 solved examples 11 practice questions

Key formulas in this chapter

The bar magnet

  • τ = m × B
  • U = −m · B
  • axis: B = (μ/4π)(2m/r), along m
  • equator: B = (μ/4π)(m/r), opposite to m
  • small oscillations: T = 2π√(I/(mB))

Gauss’s law for magnetism

  • closed surface: ∮ B · dS = 0
  • electric: ∮ E · dS = q/ε
  • flux through an element: Δϕ = B · ΔS
  • with monopoles: ∮ B · dS = μ0 qm
  • unit: 1 Wb = 1 T m

Magnetisation and magnetic intensity

  • M = mnet/V
  • H = B/μ0 − M; ideal long filled solenoid: H = nI
  • B = μ0(H + M)
  • M = χH, μr = 1 + χ
  • μ = μ0 μr, B = μH

Magnetic properties of materials

  • diamagnetic: −1 ≤ χ < 0, μ < μ
  • paramagnetic: 0 < χ ≪ 1, μ > μ
  • ferromagnetic: χ ≫ 1, μ ≫ μ
  • ideal bulk Meissner state: χ = −1, B = 0 inside
  • independent localised moments, unsaturated: χ = C/T

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