An electron moving with a velocity v 50 Times 107 ms i enter

An electron moving with a velocity v= 5.0 Times 10^7 m/s i enters a region of space where perpendicular electric and a magnetic fields are present. The electric field is E = 10^4 V/m j. What magnetic field will allow the electron to go through the region without being deflected?

Solution

As electron goes without diflected that means net force on electron is zero.

so electric force and magnetic forces are equal in magnitude but opposite in direction.

Fnet = Fe + Fb = 0

    qE + q(v X B) = 0

    E + (v x B) = 0

    10^4 j + (5e+7i x B) = 0

    B = 2 x 10^-4 (k) T

    Ans(1st Option)