# Motion of Charges in E and B Fields

1. May 4, 2012

### PatrickGeddes

1. The problem statement, all variables and given/known data
Consider and electron being ejected from the surface of a heated filament at nearly zero speed. Through what potential difference must it be accelerated to achieve a speed of 8.4x10^6 m/s?

2. Relevant equations
I have found that the equation I should be using is 1/2mv^2=eΔV (where I believe ΔV is m/e?)

3. The attempt at a solution
No attempt finding the equation is the work I have done.

2. May 4, 2012

### tiny-tim

Hi Patrick!

(try using the X2 button just above the Reply box )
yes

(but do you mean that you've worked out that this is the correct equation, or that you found it somewhere and it looks right? )
no, ∆V is the voltage difference (electric potential difference)

(V means voltage, ∆ means difference in)

3. May 14, 2012

### tracyellen

I have a question on this one...what would the mass be? You have the V and e correct but you don't have m??

4. May 14, 2012

### tracyellen

OR would the mass be just the standard electron mass at 9.11×10^-31 kg?

5. May 15, 2012

### tiny-tim

yup!

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