In an experiment, electrons are accelerated, from rest, by applying, a voltage of $500 \,V.$ Calculate the radius of the path if a magnetic field $100\,mT$ is then applied. [Charge of the electron $= 1.6 \times 10^{-19}\,C$ Mass of the electron $= 9.1 \times 10^{-31}\,kg$ ]
JEE MAIN 2019, Medium
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${{\text{k}}_{\text{e}}} = \frac{{{{\text{p}}^2}}}{{2{{\text{M}}_{\text{e}}}}} = 500\,{\text{e}} \ldots ({\text{i}})$

$\ \,{\text{R}} = \frac{{\text{p}}}{{{\text{eB}}}} = \frac{{1000{{\text{m}}_{\text{e}}}{\text{e}}}}{{{\text{eB}}}}$

$ = \frac{{1010 \times 9.1 \times {{10}^{ - 31}}}}{{1.6 \times {{10}^{ - 19}}}}$

$ = 100 \times 7.541 \times {10^{ - 6}}$

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