Question

A particle having the same charge as of electron moves in a circular path of radius 0.5 cm under the influence of a magnetic field of 0.5 T. If an electric field of 100 V/m makes it move in a straight path, then the mass of the particle is ___?
(Given charge of electron = $1.6\times {10}^{-19}C$)

• A. $2.0\times {10}^{-24}kg$
• B. $1.6\times {10}^{-19}kg$
• C. $1.6\times {10}^{-27}kg$
• D. $9.1\times {10}^{-31}kg$

Answer 1

Answer: (A)

$2.0\times {10}^{-24}kg$

$\frac{m{v}^2}{R}=qvB$
$mv=qBR$
Path is straight line
it qE = qvB
E = vB
From equation (i) & (ii)
$m=\frac{q{B}^{2}R}{E}$
$m=2.0\times {10}^{-24}kg$