Answer: 90°.
- A 90°
- B 0°
- C 180°
- D 45°
Correct answer: A. 90°
Explanation: sin θ is greatest at 90°, so the force is maximum when v is perpendicular to B.
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.