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🧪 Magnetism — Complete Theory
📖 What is Magnetism?
Magnetism is a fundamental force caused by moving electric charges. It manifests as attractive or repulsive forces between magnetic materials. Every magnet has two poles: North (N) and South (S). Opposite poles attract, like poles repel.
Magnetic Force between poles: F = μ₀ · (m₁·m₂) / (4π·r²)
🧲 Magnetic Field
The magnetic field is an invisible region around a magnet where magnetic forces act. Field lines emerge from the North pole and enter the South pole. The density of field lines indicates field strength.
Magnetic Field (B) at distance r from a pole: B = μ₀ · m / (4π·r²)
🌍 Earth's Magnetic Field
Earth's core generates a magnetic field that protects us from solar wind. A compass needle aligns with Earth's field, pointing to geographic north (which is actually a magnetic south pole!).
📐 Key Laws & Principles
- Like poles repel, unlike poles attract — Fundamental property
- Magnetic field lines never cross, form continuous loops
- Inverse-square law: Field strength ∝ 1/r²
- Dipole moment: m = pole strength × separation distance
Magnetic Flux Density (B): B = μ₀·H (μ₀ = 4π×10⁻⁷ N/A²)
🧪 Experimental Observations
• A compass needle aligns with the net magnetic field direction
• Iron filings trace invisible field lines
• Field is strongest at poles, weaker farther away
• Flipping polarity reverses the entire field direction
⚡ Applications
Electric motors, generators, MRI machines, magnetic levitation trains, compass navigation, data storage (hard drives).
🎮 Interactive Simulation
Drag the magnet to any position, move the compass to measure field strength, sprinkle iron filings to visualize field lines, and flip polarity to see the field reverse direction!
