Answer: zero.
- A zero
- B maximum
- C infinite
- D always negative
Correct answer: A. zero
Explanation: F = qvB sinθ, and sin 0° = 0, so a charge moving along B feels no force.
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.