Question

A particle of mass m, charge q and kinetic energy T enters in a transverse uniform magnetic field of induction B. After the 3 s, the kinetic energy of the particle will be
A. T
B. 4 T
C. 3 T
D. 2 T

Answer 1

Correct Answer - A
`vecF=q(vec vxxvecB)`, i.e. magnetic force is perpendicular to both velocity and magnetic field. A force `_|__(r)`, to `vecV` does no work or no power delivered by force which is `_|__(r), vecVA` hence no kinetic energy or speed will change since
`P=vecF.vecV=0`
As `vecF _|__(r),vecV_|__(r),vec(dr)`
or `dW=vecF.vec(dr)=0`