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Class 12 › Physics › Moving Charges and Magnetism
CBSE2018Class Class 12 · Physics1 Marks · Mcq✅ Verified
A charged particle is released from rest in a region of steady and uniform electric and magnetic fields, which are parallel to each other. The particle will move in a
A. circle
B. helix
C. cycloid
D. straight line
✅ Answer & Solution
✅ Correct Answer: D
Since $\vec{E} \parallel \vec{B}$, the electric field accelerates the particle along the field direction. The particle starts from rest, so initial velocity is zero.
Magnetic force $F = q(\vec{v} \times \vec{B}) = 0$ when $\vec{v} \parallel \vec{B}$.
As the particle gains velocity along $\vec{E}$ (which is $\parallel \vec{B}$), the magnetic force remains zero throughout.
Hence the particle moves in a straight line.
