Question

A proton is projected with a velocity ${10}^{7}m{s}^{-1}$ , at right angles to a uniform magnetic field of induction 100 mT. The time (in seconds ) taken by the proton to traverse 90${}^0$ arc is
(Mass of proton $=1.65\times {10}^{-27}$ kg and charge of proton $=1.6\times {10}^{-19}$C )

• A. $0.81\times {10}^{-7}$
• B. $1.62\times {10}^{-7}$
• C. $2.43\times {10}^{-7}$
• D. $3.24\times {10}^{-7}$

Answer 1

The correct option is B $1.62\times {10}^{-7}$

$t=\frac{\theta m}{qB}$
$=\frac{\pi }{2}\times \frac{1\cdot 65\times {10}^{-27}}{1\cdot 6\times {10}^{-19}\times {10}^{-1}}$
$=1\cdot 62\times {10}^{-7}$