Magnetic Field and Electromagnetism

🟢 Lite — Quick Review (1h–1d)

Rapid summary for last-minute revision before your exam.

Magnetism — Key Facts Earth’s magnetic field: horizontal component B_H = B cosθ; angle of dip δ = tan⁻¹(B_V/B_H) Dia/Para/Ferro: diamagnetic (weak repulsion, no permanent moment), paramagnetic (weak attraction, aligned by field), ferromagnetic (strong, permanent magnets) Curie Law: χ = C/T for paramagnetic; Curie temperature T_C: above T_C, ferromagnet becomes paramagnet ⚡ Exam tip: Soft iron has high permeability → good for electromagnets; steel has high coercivity → good for permanent magnets

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🟡 Standard — Regular Study (2d–2mo)

Standard content for students with a few days to months.

Magnetism — NEET/JEE Study Guide Hysteresis: B lags behind H; hysteresis loop area = energy loss per unit volume per cycle; soft iron (narrow loop → low loss) Magnetic materials: hard (steel) → wide loop, high coercivity, permanent magnets; soft (soft iron) → narrow loop, low coercivity, electromagnets Magnetic screening: ferromagnetic shell shields interior from external fields (like Faraday cage for magnetism)

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🔴 Extended — Deep Study (3mo+)

Comprehensive coverage for students on a longer study timeline.

Magnetism — Comprehensive Notes Origin of magnetism: orbital and spin magnetic moments of electrons; Bohr magneton μ_B = eh/4πm Domain theory: ferromagnetism due to parallel alignment of magnetic moments in domains below Curie temperature Magnetisation M = magnetic moment per unit volume; magnetic intensity H; B = μ₀(H + M); χ = M/H; μ = μ₀(1+χ) Magnetic circuits: Φ = MMF/reluctance; analogy with Ohm’s law; magnetomotive force (MMF) = NI

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