What Speed Do Electrons Reach in a TV Tube?

  • Thread starter Myr73
  • Start date
  • Tags
    Electron
  • #1
Myr73
120
0
Electrons leave the cathode of a tv tube at essentially zero speed and are accelerated toward the front by 10, 000 V potential. At what speed do they strike the screen? Express this value also as a fraction of the speed of light.

I found-
vi=0 m/s V=10 000 V q=-1.6 X 10^-19 C (not sure if it's negative)
m= 9.1 X 10^-31 kg vf= ?(speed of light)
v(light)= 3.00 X 10^8 m/s


Delta PE= qV=(-1.6 X 10^-19 C) ( 10 000 V) = -1.6 X 10^-15 J
And then --> Delta KE= -Delta PE --> 0.5mv^2=1.6 X 10^-15
vf= SqRt{ 2(1.6 X 10^-15)/9.1 X 10^-31 = 59 295 868= 5.9 x 10^7 m/s

Fraction of speed of light --> vf/v(light)= 0.197

I am unsure if I am doing this properly-Just looking for some confirmation
 
Physics news on Phys.org
  • #2
It looks correct.

ehild
 
  • #3
You might have included relativistic effects. At 0.2c the error is about 2%. So admittedly it's not much.
 
  • #4
Awesome-
 
Back
Top