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Calculating Electric Potenial Difference

  • Thread starter chef99
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  • #1
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Homework Statement


In a TV tube, an electric potential difference accelerates electrons from a rest position towards a screen. Just before striking the screen, the electrons have a wavelength of 1.0 x10-11m. Find the electric potential difference.[/B]

Homework Equations


λ = h/mv

Ek = qΔV

The Attempt at a Solution


[/B]
First, determine the velocity

λ = h/mv

v = h/λm

v = 6.63 x10-34J / (1.0 x10-11m)(9.11 x10-31m/s)

v = 7.28 x10-7


Now determine the electric potential difference

Ek = qΔV

1/2 mv2 = eΔV

V = 1/2 mv2 /eΔ

V = 1/2 (9.11 x10-31kg)(7.28 x10-7m/s)2 / (1.60 x10-19C)


V = 1.51 x10-24

The electric potential difference is 1.51 x10-24 V right before the electron strikes the screen.

I am fairly confident in my methods/answer but I haven't had to calculate the electric potential difference before so I just want to make sure I have the right idea. Any feedback would be great.
 

Answers and Replies

  • #2
Charles Link
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For the velocity, you put an extra minus sign in the exponent. It should be +7. Otherwise, your methodology is correct.
 
  • #3
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For the velocity, you put an extra minus sign in the exponent. It should be +7. Otherwise, your methodology is correct.
Oh wow, thank you for catching that.

So the electric potential difference is actually 1.51 x10-4
 
  • #4
Charles Link
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Oh wow, thank you for catching that.

So the electric potential difference is actually 1.51 x10-4
Try the arithmetic again. I get ## V=1.51 \cdot 10^{+4} ## volts.
 

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