Cyclotron
A particle accelerator using a perpendicular magnetic field to accelerate charged particles in a spiral path. Particles move in semicircles of increasing radius as they gain energy, crossing a gap where an electric field accelerates them each half-cycle.
Formula
r = mv/(qB)
Real World
Ernest Lawrence built the first cyclotron at Berkeley in 1930 to accelerate protons; modern medical cyclotrons in hospitals produce the radioactive tracers used in PET scans for cancer diagnosis.
Exam Focus
When asked to 'explain' why frequency is independent of speed, link r ∝ v and T = 2πr/v to show the v cancels — this is a common 4-mark explain question.
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