Answer: theta = 0 degrees.
- A theta = 90 degrees
- B theta = 45 degrees
- C theta = 0 degrees
- D F is never zero
Correct answer: C. theta = 0 degrees
Explanation: F = BIL sin(theta) = 0 when sin(theta) = 0, i.e., theta = 0 degrees. When current is parallel to B, 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.