Question

An electron has an initial velocity of (11.0j + 15.0k) km/s and a constant acceleration of (1.00×10¹²m/s²)i in a region in which uniform electric and magnetic fields are present. If B =(400?T)i, find the electric field E.

Ey?

Ez?

Answer 1

Force on electron in a magnetic field

F1 = q*(VxB) = q*[ (11 j + 15 k)*10^3x(400*10^-6 i )] = q*[ -4400 k + 6000 j ]*10^-3

=> F1 = 1.602*10^-19*[ -4400 k + 6000 j ]*10^-3 = [ - 7.04 k + 9.61 j ]*10^-19

and external force F2 = m*a = 9.1*10^-31*10^12 i = 9.1*10^-19 i  

=> Net force on electron Fnet = F1+F2 = ( 9.1 i + 9.61 j - 7.04 k )*10^-19 N

=> Electric field , E = Fnet / q =  ( 9.1 i + 9.61 j - 7.04 k )*10^-19 /(1.602*10^-19) = 5.68 i + 5.998 j - 4.39 j

=> Ey = 5.998 N/C , Ez = - 4.39 N/C