Q. In a chamber, a uniform magnetic field of $6.5 \,G$ $\left(1\, G =10^{-4} T \right)$ is maintained. An electron is shot into the field with a speed of $4.8 \times 10^{6} ms ^{-1}$ normal to the field. Determine the radius of the circular orbit.
$\left( e =1.6 \times 10^{-19} C , m _{ e }=9.1 \times 10^{-31} kg \right)$

Solution:

Correct answer is (d) 4.2 cm