Question

A charged particle is moving in a circular orbit in a magnetic field. If the strength of the magnetic field becomes four times, Find out the change in radius of the particle's orbit.

• 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 A It is quartered

Using $Bqr=mv$ $⟹r=\frac{mv}{Bq}$

Now the magnetic field is increased to 4 times i.e $B^{\prime }=4B$

$\therefore$ New radius $r^{\prime }=\frac{mv}{B^{\prime }q}=\frac{mv}{\left(4B\right)q}=\frac{r}{4}$

Thus the radius is quartered.