# Calculating Electric Potenial Difference

## 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]

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.

Related Introductory Physics Homework Help News on Phys.org
Homework Helper
Gold Member
For the velocity, you put an extra minus sign in the exponent. It should be +7. Otherwise, your methodology is correct.

• chef99
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

Try the arithmetic again. I get $V=1.51 \cdot 10^{+4}$ volts.
• 