A particle of charge +q and mass m moving under the influence of a uniform electric field E and unif

Question

A particle of charge +q and mass m moving under the influence of a uniform electric field E

and uniform magnetic field B

follows a trajectory from P to Q as shown in figure. The velocities at P and Q are

and

. Which of the following statement(s) is /are correct ?

Accepted Answer

Magnetic force does not do work. From work energy theorem :
W_{F_e} = ᐃ KE or (qE)(2a) =

m[4v² - v²]
or E =

∴ Correct option is (a).
At P, rate or work done by electric field
=

= (qE) (v) cos0^o

Therefore, option (b) is also correct.
Rate of work done at Q :
of electric field =

= (qE) (v) cos 90^o = 0
and of magnetic field is always zero. Therefor, option (d) is also correct.

Question