Relativistic physics?

Question

Initially at rest,an electron emerges from a potential difference of 100 kV with a speed comparable to the speed of light.

using relativistic mechanics what is the final speed of the electron

Answer 1

qV = relativistic translational kinetic energy formula

q = charge of the electron
V = potential difference (i.e. 100kV)

solve for v, velocity

Answer 2

After passing through the potential difference, the electron has an energy equal to (charge)x(potential difference). That is,

E = qV

where q is the electron's charge, and V is 100 kV.

Relativistic mechanics says,

E = mc²

so qV = mc²

The value of m is a function of the electron's rest mass, and of velocity. You should know this formula. Then just use algebra to solve for velocity.

Answer 3

Actually electrons travel at about 1/3 the speed of light. It's just the ammount of electrons moving that affect the current. More resistance or resistivity of a conductor, means less current, less electrons & less energy. Its only relative to variables, legnth, diameter, temperature etc.
Eamonn.