Magnetism and Matter Class 12 Physics Notes – Formulas & Quick Revision

Magnetism and Matter mein bar magnet, earth ka magnetism aur magnetic materials ki classification aati hai. Yahan aapko is chapter ke sabse important formulas aur quick revision points free milte hain — NCERT/CBSE syllabus ke hisaab se, boards aur JEE/NEET dono ke liye.

Important Formulas & Concepts — Magnetism and Matter

• Magnetic moment m = NIA
• Bar magnet: B_axial = μ₀2m/4πr³; B_equatorial = μ₀m/4πr³
• Torque: τ = mB·sinθ; U = −mB·cosθ
• χ (susceptibility): dia −ve, para +ve small, ferro +ve large
• B = μ₀(H + M); μᵣ = 1 + χ
• Curie law: χ ∝ 1/T
• Earth: B_H = B·cosδ (δ = dip angle)
• tanδ = B_V/B_H

Quick Revision Points

• Diamagnetic: repelled (Cu, Bi, water); paramagnetic: weakly attracted (Al, Na); ferromagnetic: strongly (Fe, Co, Ni)
• Ferromagnet Curie temperature ke upar paramagnet ban jata hai
• Magnetic field lines closed loops hoti hain (monopole nahi hota)
• Dip angle poles par 90°, equator par 0°
• Hysteresis loop area = energy loss per cycle

FAQ

Materials ki classification kaise yaad rakhun?

PDF mein dia/para/ferro ki comparison table hai — χ, μᵣ, examples sab ek saath.

Ye chapter kitna weightage rakhta hai?

Chhota hai — 2-3 marks — par NEET mein material classification pakka aata hai.

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