An electron is moving along positive x-axis `A` unifrom electric field exists towards negative y-axis. What should be the direction of magnetic field of suitable magnitude so that net force of electrons is zero .

Options

A. positive z- axis
B. negative z-axis
C. positive y-axis
D. negative y-axis

Answer

A

Explanation

Velocity of electron`=v hati`
Magnetic field `=-Bhatj`
Force by Magnetic field `=q(vecVxxvecB)=-e(hatixxvecB(-hatj))=(evB)hatk`
Hence, Electric field should be along positive z axis.