# Electric Fields Problem

• rhettfraser

## 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 don't know where to start

Welcome to PF!

Hi rhettfraser! Welcome to PF!

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

Hi rhettfraser! Welcome to PF!

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

thanks

Hi rhettfraser! Welcome to PF!

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

but how do you find the force?

uhh? you don't, you use ∫ electric-field"dot"charge

uhh? you don't, you use ∫ electric-field"dot"charge

ok now I've 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?

Conservation of energy … KE + PE = constant

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