Question

The electrons in a particle beam each have a kinetic energy of 1.6x10^-16J. The magnitude of the electric field that would stop the electrons in a distance of 1 m is what?

Answer 1

Work done by the Electric field in stopping the electron in a distance 1m is W= q*E*d

here q is charge of electron = -1.6*10^-19 C

E is the required electric field

d is the distance = 1m

but this is equal to change in Kinetic energy according to work energy theorem

Work done = change in KE = Kf-Ki

Kf = 0.5*m*Vf^2 = 0    J

Ki = 1.6*10^-16 J

then W = -1.6*10^-19

q*E*d = -1.6*10^-16

-1.6*10^-19*E*1 = -1.6*10^-16

required electric field is E= 10^3 N/C or V/m