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Electric Fields Problem

  • #1

Homework Statement


An electron is accelerated from the filament in a vacuum tube towards a metal grid which is maintained at a potential of 180 Volts. It goes through one of the holes in the grid and continues towards a metal plate 1.2 cm away which is maintained at a potential of -10.0 Volts.

How close to the plate does the electron get?


Homework Equations



Im not sure, maybe something to do with Potential Difference

The Attempt at a Solution



I dont know where to start
 

Answers and Replies

  • #2
tiny-tim
Science Advisor
Homework Helper
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Welcome to PF!

Hi rhettfraser! Welcome to PF! :smile:

Hint: work done = ∫ force"dot"distance = ∫ electric-field"dot"charge, and the electron will stop when the KE is zero. :wink:
 
  • #3


Hi rhettfraser! Welcome to PF! :smile:

Hint: work done = ∫ force"dot"distance = ∫ electric-field"dot"charge, and the electron will stop when the KE is zero. :wink:
thanks
 
  • #4


Hi rhettfraser! Welcome to PF! :smile:

Hint: work done = ∫ force"dot"distance = ∫ electric-field"dot"charge, and the electron will stop when the KE is zero. :wink:
but how do you find the force?
 
  • #5
tiny-tim
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Homework Helper
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uhh? you don't, you use ∫ electric-field"dot"charge :smile:
 
  • #6
uhh? you don't, you use ∫ electric-field"dot"charge :smile:
ok now ive worked out that the work done is 3.04x10-17
how should i work out that when KE is zero the electron will stop?
I know that W= Change in PE, is there anyway that W is related to KE?
 
  • #7
tiny-tim
Science Advisor
Homework Helper
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Conservation of energy … KE + PE = constant :smile:

(or work-energy theorem …KE + W = constant)
 

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