Q. When a charged particle moving with velocity v⃗ is subjected to a magnetic field of induction B⃗, the force on it is non-zero. This implies that :
A) angle between v⃗ and B⃗ is necessarily 90°
B) angle between v⃗ and B⃗ can have any value other than 90°
C) angle between v⃗ and B⃗ can have any value other than zero and 180°
D) angle between v⃗ and B⃗ is either zero or 180°
Explanation
[Solution from source] The magnetic force is F = qvB sin θ, which vanishes only when θ = 0° or 180°. So a non-zero force tells us only that θ is anything other than 0° and 180°. It need not be exactly 90°; 90° simply gives the maximum force. Answer (3).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.