Department of Pre-University Education, KarnatakaPUC Karnataka Science Class 12

# A Particle Moves in a Region with a Uniform Magnetic Field and a Parallel, Uniform Electric Field. at Some Instant, the Velocity of the Particle is Perpendicular to - Physics

MCQ

A particle moves in a region with a uniform magnetic field and a parallel, uniform electric field. At some instant, the velocity of the particle is perpendicular to the field direction. The path of the particle will be

#### Options

• a straight line

•  a circle

• a helix with uniform pitch

•  a helix with non-uniform pitch

#### Solution

a helix with non-uniform pitch

Here, the total Lorentz force on the particle,

F = qE + qVB

We all know that magnetic field B does not change the speed of the particle but changes its direction. But as an electric field is also present that accelerate the particle in the direction of the field, the resultant path is a helix with a non-uniform pitch.

Concept: Force on a Current - Carrying Conductor in a Uniform Magnetic Field
Is there an error in this question or solution?

#### APPEARS IN

HC Verma Class 11, Class 12 Concepts of Physics Vol. 2
Chapter 12 Magnetic Field
MCQ | Q 9 | Page 229