Answer: mv/qB.
- A mv/qB
- B qB/mv
- C mvB/q
- D qvB/m
Correct answer: A. mv/qB
Explanation: Equating qvB = mv²/r gives r = mv/qB.
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.