Question

A proton of mass $m$ and charge $e$ is fired parallel to a uniform magnetic field of induction $B$. The radius of curvature of the path of the particle in the field is

• A. $\frac{Be}{mv}$
• B. $\frac{mv}{Be}$
• C. $0$
• D. $\infty$

Answer 1

Answer: (D)

$\infty$

$F=q(\overrightarrow{V}\times \overrightarrow{B})$
$\theta =0^o$
$F=0$
It will keep moving in its initial direction.
So $r=\infty$