Steering Charged Particles

Velocity selectors, spectrometers, cyclotrons

An interactive lesson with 7 steps, about 6 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• A magnetic force turns charges without changing their speed: circles of radius $r = mv/qB$.
• Crossed fields select one speed, $v = E/B$; spectrometers then sort by mass.
• The lap time $2\pi m/qB$ doesn't depend on speed, which makes the cyclotron work.

Steps

1. Light or heavy?
2. The velocity selector
3. Pick the speed
4. Weighing an atom
5. Separating isotopes
6. The cyclotron
7. Cyclotron frequency