Question

An electron moving with a velocity of 15 ms^-1 enters a uniform magnetic field of 0.2 T, along a direction parallel to the field. What would be its trajectory in this field?

(a) Elliptical

(b) Straight path

(c) Helical

(d) Circular

This question was addressed to me in an online quiz.

Origin of the question is Motion in a Magnetic Field in division Moving Charges and Magnetism of Physics – Class 12

Answer 1

Correct choice is (b) Straight path

To elaborate: The electron will continue to follow its straight path because a parallel magnetic field does not exert any force on the electron. So, there won’t be any change in its trajectory when the electron enters a uniform magnetic field.