Question

A charged particle is moving in a circular orbit in a magnetic field. If the strength of the magnetic field doubles, how does the radius of the particles orbit change?

• A. It is quartered
• B. It is halved
• C. It is unchanged
• D. It is doubled
• E. It is quadrupled

Answer 1

The correct option is B It is halved

Initial radius of the orbit $r=\frac{mv}{Bq}$

New strength of magnetic field $B^{\prime }=2B$

Thus radius of new orbit $r^{\prime }=\frac{mv}{\left(2B\right)q}=\frac{r}{2}$