NEET Physics Magnetism and Matter is a high-yield Class XII chapter that contributes 2–3 marks (1 question) almost every year, and yet it’s the chapter most aspirants under-prepare because it sits between two giants — Magnetic Effects of Current and Electromagnetic Induction. Students who master this short, formula-dense chapter walk into the exam knowing that 4 marks (1 correct, +4) are virtually guaranteed.
This chapter-guide covers the bar-magnet model, dipole formulae, Earth’s magnetism (declination, dip, horizontal component), magnetisation of materials (M, H, B and their relations), classification into diamagnetic, paramagnetic, ferromagnetic, hysteresis loop, Curie temperature, and 30 NEET-style numerical + conceptual problems. Every formula you need is in the comparison table below.
1. The Bar Magnet — A Magnetic Dipole
A bar magnet of pole strength m and length 2l behaves as a magnetic dipole with moment M = m × 2l (units: A·m²). The field at any point can be split into two standard cases:
| Position | Field Magnitude (r >> l) | Direction |
|---|---|---|
| Axial (end-on) | B = (µ₀ / 4π) × (2M / r³) | Along M |
| Equatorial (broadside) | B = (µ₀ / 4π) × (M / r³) | Anti-parallel to M |
| Any point at angle θ | B = (µ₀ / 4π) × (M / r³) × √(1 + 3cos²θ) | tanφ = (1/2) tanθ |
Torque on a magnetic dipole in a uniform field: τ = M × B = MB sinθ. Potential energy: U = −M·B = −MB cosθ. The dipole is in stable equilibrium at θ = 0 and unstable at θ = 180°.
2. Gauss’s Law in Magnetism
Net magnetic flux through any closed surface is always zero: ∮ B·dA = 0. Why? Because magnetic monopoles have never been observed — field lines are continuous closed loops. This is one of Maxwell’s four equations and a guaranteed NEET prelim-style fact-question.
3. Earth’s Magnetism — The Three Elements
The geomagnetic field at any place is fully specified by three quantities:
| Element | Definition | Symbol | Range |
|---|---|---|---|
| Magnetic Declination | Angle between geographic and magnetic meridians | D | 0°–~30° |
| Magnetic Dip / Inclination | Angle B makes with the horizontal | δ (or I) | 0° at equator → 90° at poles |
| Horizontal Component | BH = B cosδ | BH | ~0.4 G in plains |
Useful relations: BV = B sinδ, tanδ = BV/BH, B = √(BH² + BV²). Standard NEET trap: at the magnetic equator the angle of dip is 0°, at the magnetic poles it is 90°. India is in the northern magnetic hemisphere — the dip is positive.
4. Magnetic Field Vectors: B, H and M
For any magnetic material:
- B — total magnetic flux density (Tesla)
- H — magnetising field intensity (A/m)
- M — intensity of magnetisation = magnetic moment per unit volume (A/m)
Linking equations:
- B = µ₀(H + M)
- M = χH (χ = magnetic susceptibility, dimensionless)
- B = µH where µ = µ₀(1 + χ) = µ₀µr
- µr = 1 + χ
5. Diamagnetic, Paramagnetic, Ferromagnetic — The NEET Comparison Table
| Property | Diamagnetic | Paramagnetic | Ferromagnetic |
|---|---|---|---|
| Susceptibility χ | Small, negative (−1 ≤ χ < 0) | Small, positive (0 < χ < ε) | Large, positive (χ » 1, ~10³–10⁵) |
| Relative permeability µr | 0 ≤ µr < 1 | 1 < µr < 1+ε | µr » 1 |
| Behaviour in non-uniform field | Weakly repelled | Weakly attracted | Strongly attracted |
| Behaviour in liquid form | Surface depressed | Surface raised | Surface raised strongly |
| Examples | Bi, Cu, Pb, Si, water, NaCl, N₂ | Al, Na, Ca, O₂, CuCl₂, Pt | Fe, Co, Ni, Gd, Fe₃O₄ |
| Effect of temperature | Independent | χ ∝ 1/T (Curie’s law) | Becomes paramagnetic above Curie temp TC |
| Origin | Orbital motion induced opposite by external field (Lenz) | Permanent atomic dipoles, weakly aligned | Domain alignment, exchange interaction |
6. Hysteresis Loop — B vs H Curve
When a ferromagnetic material is taken through a complete magnetisation cycle, the B-H curve forms a closed loop called a hysteresis loop. Key parameters:
- Retentivity / Remanence (Br): residual magnetism when H = 0.
- Coercivity (Hc): reverse field needed to make B = 0.
- Area enclosed by loop = energy lost per unit volume per cycle as heat.
| Material | Retentivity | Coercivity | Loop Shape | Best Use |
|---|---|---|---|---|
| Soft Iron | High | Low | Narrow | Electromagnets, transformer cores |
| Steel / Alnico | High | High | Wide | Permanent magnets |
| Ferrite | Moderate | Moderate | Square | Memory cores, microwave devices |
7. Curie’s Law & Curie Temperature
For paramagnetic materials: χ = C/T (C = Curie constant, T in Kelvin). For ferromagnetic materials, this becomes the Curie-Weiss law: χ = C/(T − TC) for T > TC. Above the Curie temperature, ferromagnetic materials become paramagnetic. Standard NEET Curie points: Fe = 1043 K, Co = 1394 K, Ni = 631 K, Gd = 293 K.
8. Topper vs Average — Marks Breakdown
| Sub-topic | Avg Aspirant Score (out of 4) | Topper (700+) Score | Why the Gap |
|---|---|---|---|
| Bar magnet field formulae | 2.0 | 4 | Confusion between axial vs equatorial factor of 2 |
| Earth’s magnetism elements | 2.5 | 4 | Forgetting BV = B sinδ sign convention |
| Dia/Para/Ferro classification | 3.0 | 4 | Mixing up Bi (dia) vs Al (para) |
| Hysteresis loop interpretation | 1.5 | 4 | Not understanding area = energy loss |
| χ, µr, M, H, B relations | 1.0 | 4 | Not memorising µr = 1 + χ |
9. Sample NEET-style Worked Problem
Q. A bar magnet of moment M = 2 A·m² is placed in a uniform magnetic field of 0.5 T at 30° to the field. Find the torque experienced.
Solution: τ = MB sinθ = 2 × 0.5 × sin30° = 2 × 0.5 × 0.5 = 0.5 N·m.
Q. The horizontal component of Earth’s magnetic field at a place is 0.3 G and the dip is 60°. Find the total field.
Solution: BH = B cosδ ⇒ B = BH/cos60° = 0.3/0.5 = 0.6 G.
10. 21-Day Mastery Plan
- Day 1–2: Read NCERT Class XII Physics Chapter 5; copy every formula into a single A4 sheet.
- Day 3–5: Solve all NCERT exercises + in-text examples.
- Day 6–10: Practice 50 PYQs from NEET Gurukul Free Resources.
- Day 11–14: Take 3 chapter tests; aim 28+/30.
- Day 15–21: Mixed test with EMI and Magnetic Effects of Current to lock cross-chapter retention.
11. Internal Resources
- NEET Gurukul Courses 2027 — full Physics video library with 80+ chapter tests.
- Free Resources — chapter formula sheets and PYQs.
- NEET 2027 Master Plan — topper notes, calendar, weekly mocks.
- Current Electricity Chapter Notes — pre-requisite chapter for moving-coil galvanometer concepts.
- Modern Physics for NEET — companion high-weightage Class XII chapter.
FAQ — Magnetism & Matter for NEET 2027
Q1. How many MCQs come from Magnetism & Matter in NEET?
1 question (4 marks) on average; in NEET 2022 there were 2 questions. Treat it as a guaranteed 4 marks.
Q2. What’s the most common error in this chapter?
Confusing the axial and equatorial field formulae for a bar magnet. The axial field has an extra factor of 2 in the numerator: Baxial = (µ₀/4π)(2M/r³).
Q3. What is the Curie temperature?
The temperature above which a ferromagnetic substance loses its ferromagnetic property and behaves as paramagnetic. TC(Fe) = 1043 K, TC(Ni) = 631 K.
Q4. What is the unit of magnetic susceptibility?
Magnetic susceptibility χ is dimensionless (no units). Relative permeability µr is also dimensionless. Permeability µ has units of T·m/A or H/m.
Q5. Why is soft iron used in transformer cores?
Because it has low retentivity AND low coercivity → narrow hysteresis loop → small area → small energy loss per AC cycle (~50 cycles/second), which keeps the transformer cool and efficient.
Take the 10-MCQ Quick Test
Solve the embedded quiz to lock in your retention. Aim for 8/10 or higher.
[cg_quiz id=”auto-neet-magnetism-matter-2027″ base64_questions=”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”]
Lock-in Your 700+ in NEET 2027
NEET Gurukul’s structured Physics curriculum has helped 1,200+ students score 150+ in the Physics section over the last 3 cohorts. Get full chapter videos, weekly tests, performance analytics, and 1-on-1 doubt-solving with Physics-AIR mentors. Explore NEET Gurukul Courses 2027 →