Question

An electron having kinetic energy $10 \, eV$ is circulating in a path of radius $0.1 \, m$ in an external magnetic field of intensity $10^{- 4} \, T$ . The speed of the electron will be

• A. $1.76 \times\left(10^6\right) \mathrm{ms}^{-1}$
• B. $4.8 \times\left(10^6\right) \mathrm{ms}^{-1}$
• C. $2.0 \times\left(10^{12}\right) \mathrm{ms}^{-1}$
• D. $4.8 \times\left(10^{12}\right) \mathrm{ms}^{-1}$

Answer 1

Answer: (A)

When charge enters into a perpendicular magnetic field, it starts to move in a circular path.
Radius of a circular path followed by a charge particle:
$r = \frac{m V}{q B}$
$V=1.76 \times\left(10^6\right) \mathrm{ms}^{-1}$