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 a 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)

$2.84$

Given : $m=9.1\times {10}^{-31}kg$ $e=1.6\times {10}^{-19}C$ $v={10}^{6}m/s$
Radius of circular path $r=0.2m$
Intensity of magnetic field $B=\frac{mv}{er}$
$⟹B=\frac{9.1\times {10}^{-31}\times {10}^6}{1.6\times {10}^{-19}\times 0.2}=2.84\times {10}^{-5}T$
Correct answer is option C.