A charged particle starts from rest in a region where uniform, time-independent electric and magnetic fields are present and both fields point in the same direction. The particle’s path will be

a straight path
a circular path
a helical path
a cycloidal path

Correct answer: a straight path

Solution

From rest, only E acts initially, accelerating the particle along B. Since the velocity stays parallel to B, the magnetic force qv x B is always zero, so the path is a straight line along the field.

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