Question

An electron having mass $9.1 \times 10^{-31} kg$, charge $1.6 \times 10^{-19}$ $C$ and moving with the velocity of $10^{6} m / s$ enters are region where magnetic field exists. If it describes a circle of radius $0.2\, m$ then the intensity of magnetic field must be ________$\times 10^{-5} T$.

• A. 14.4
• B. 5.65
• C. 2.84
• D. 1.32

Answer 1

Answer: (C)

$R=\frac{m v}{q B} \Rightarrow B=\frac{m v}{q R}$
$B=\frac{9.1 \times 10^{-31} \times 10^{6}}{1.6 \times 10^{-19} \times 0.2}$
$=\frac{9.1}{1.6 \times 2} \times 10^{-6}$
$=2.84 \times 10^{-6} T$