Question

A $10eV$ electron is circulating in a plane at right angles to a uniform field at a magnetic induction ${10}^{-4}Wb/m^2(=1.0gauss)$. The orbital radius of the electron is

• A. 12 cm
• B. 16 cm
• C. 11 cm
• D. 18 cm

Answer 1

The correct option is C 11 cm

Given : $K=10eV$ $B={10}^{-4}$ $Wb/m^2$

Using : $mv=Bqr$ where $mv=\sqrt{2Km}$

$⟹$$r=\sqrt{\frac{2Km}{B^2{q}^2}}$

$\therefore$ $r=\sqrt{\frac{2\times 9.1\times {10}^{-31}\times 10e}{\left({10}^{-8}\right)e^2}}=1.06\times {10}^{-2}m$ $\approx 11cm$