Question

The diagram above shows a positively charged particle moving toward the right and about to enter a magnetic field whose direction is shown by the blue arrows.
What is the direction of the force on the positively charged particle (from our point of view) at the instant it enters the magnetic field?

• A. Right
• B. Left
• C. Up
• D. Toward us
• E. Away from us

Answer 1

The correct option is E Away from us

Given : $\overrightarrow{v}=v\hat{x}$ $\overrightarrow{B}=-B\hat{y}$

Magnetic force $\overrightarrow{F}=q(\overrightarrow{v}\times \overrightarrow{B})=q[v\hat{x}\times (-B\left)\hat{y}\right]=-qvB$ $\hat{z}$

Thus the charge particle experience a magnetic force in a direction away from us.