question_answer

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 \[=1.6\times {{10}^{-16}}C,\] Mass of the electron \[=9.1\times {{10}^{-31}}kg\]]                                                        [JEE Main 11-Jan-2019 Morning]

A) \[7.5m\]

B) \[7.5\times {{10}^{-2}}m\]

C) \[7.5\times {{10}^{-4}}m\]

D) \[7.5\times {{10}^{-3}}m\]

Correct Answer: C

Solution :

[c] The velocity acquired by the electron is given as follows :

when the particle enters the magnetic field its speed remains unchanged