An electron enters a uniform magnetic field B=B₀j . . .

Question : An electron enters a uniform magnetic field B=B₀j with its initial velocity V=8×104 i m/s. Direction of magnetic force experience by the electron is :

a) along positive z-axis

b) along x-axis

c) along y-axis

d) along negative z-axis. 

Doubt by Angad

Solution : 

B=B₀j T

V=8×104 i m/s

We know, 

F = q(V×B)

F = q(vi×Bj)
F = qvB(i×j)
F = qvB k [∵i×j=k]

Hence the direction of magnetic force will be along k i.e. positive direction of z-axis.

Hence, a) along positive z-axis, is correct option.