Magnetic field
A region of space where a magnetic force is exerted on a moving charge or current-carrying conductor. Magnetic field strength (or magnetic flux density) B is measured in tesla (T), where 1 T = 1 N/(A·m). Magnetic field is represented by field lines showing direction (from north to south pole of a magnet). The force on a moving charge in a magnetic field is F = qvB sin θ (where θ is the angle between velocity and field), directed perpendicular to both v and B (given by the right-hand rule).
Formula
F = BqvsinΘ
Real World
The Large Hadron Collider at CERN uses thousands of superconducting dipole magnets producing fields of ~8 T to bend proton beams into circular paths at near-light speed, exploiting the perpendicular magnetic force on moving charges.
Exam Focus
Use Fleming's left-hand rule and state which finger represents which quantity — losing a direction mark is common when the rule is applied without explanation.
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