Answer: speed.
- A speed
- B charge
- C mass
- D field strength
Correct answer: A. speed
Explanation: T depends on m, q and B but not on the speed, which is why a cyclotron works.
The magnetic field around a long straight current-carrying wire forms concentric circles, with direction given by the right-hand rule (point thumb along I, fingers curl in the direction of B).
Concept context
Magnetic force on moving charges and currents, the Biot-Savart law, Ampere's law, and the cyclotron - how electric currents create and respond to magnetic fields.