Question

A uniform magnetic field is at right angles to the direction of motion of protons. As a result the protons describes a circular path of radius $2.5cm$. If the speed of the protons is doubled, then the radius of the circular path will be

• A. $0.5cm$
• B. $2.5cm$
• C. $5.0cm$
• D. $7.5cm$

Answer 1

The correct option is C $5.0cm$

$R=\frac{mv}{Bq}$
$R$ is proportional to $v$
if $V$ is doubled, $R$ is also doubled.