Answer: 1:2.
- A 1:2
- B 2:1
- C 1:1
- D 1:4
Correct answer: A. 1:2
Explanation: r = mv/(qB). malpha = 4mp, qalpha = 2qp. ralpha = 4mp x v/(2qp B) = 2rp. Ratio rp:ralpha = 1:2.
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.