Discussion Forum

An electron and a proton are moving on shaight parallel paths with same velocity. They enter a semi-infinite region of uniform magnetic field perpendicular to the velocity. Which of the following statement(s) is/are true?

Answer:

Explanation:

 $r= \frac{mv}{Bq}$

 or   $r \propto m$

 $\therefore$    $r_{e} <r_{p}$  as $m_{e}< m_{p}$

 Further  , $T = \frac{2 \pi m}{Bq}$

 or  $T \propto m$

 $\therefore$   $T_{e} <T_{p}$

 $t_{e} = \frac{ T_{e}}{2}$

 and $t_{p}=\frac{ T_{P}}{2}$

 or   $t_{e}  < t_{p}$

 $\therefore$   Correct options are (b) and (d) 

Note In JEE 2011, official answer key' correct oPtions were given bc, bd, bcd, here student should realise that both the electron and Proton enter the magnetic field at the same time or at different times

Analysis of Question
(i) Question is simPle'
(ii) In the situation given above particle
will never complete the circle unless
the magnetic field is all around