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Electric Potential Energy

 
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Sep23-08, 01:24 PM   #1
 
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Electric Potential Energy

An electron and a proton are initially very far apart (effectively an infinite distance apart). They are then brought together to form a hydrogen atom, in which the electron orbits the proton at an average distance of 5.43 * 10-11 m. What is EPEfinal - EPEinitial, which is the change in the electric potential energy?

I have no idea where to start
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Sep23-08, 02:09 PM   #2
 
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Quote by nckaytee View Post
An electron and a proton are initially very far apart (effectively an infinite distance apart). They are then brought together to form a hydrogen atom, in which the electron orbits the proton at an average distance of 5.43 * 10-11 m. What is EPEfinal - EPEinitial, which is the change in the electric potential energy?

I have no idea where to start
Isn't the potential energy given by PE = kq1*q2/r

If EPE at infinity is 0, then ... The change is ...
Sep23-08, 03:32 PM   #3
 
In my notes I have [tex]\Delta E.P.E[/tex] of electron = q(Vb-Va) = (-e)(Vb-Va)

I am really not getting this


Im sorry, I might have something here... One minute..
Sep23-08, 03:44 PM   #4
 

Electric Potential Energy

Okay I am confused
Sep23-08, 03:57 PM   #5
 
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Quote by nckaytee View Post
In my notes I have [tex]\Delta E.P.E[/tex] of electron = q(Vb-Va) = (-e)(Vb-Va)

I am really not getting this


Im sorry, I might have something here... One minute..
What is the charge of an electron and a proton?

Quote by Wikipedia
e = –1.602176487(40) × 10–19C
p = 1.60217653(14)×10−19 C
Sep23-08, 04:00 PM   #6
 
So, would it be...

(-1.6*10^19)(0 - 5.43 *10^-11)
Sep23-08, 04:03 PM   #7
 
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Quote by nckaytee View Post
So, would it be...

(-1.6*10^19)(0 - 5.43 *10^-11)
It's the product of both charges.

PE = kq1*q2/r


And check the exponent of the charges. And don't forget k.
Sep23-08, 04:18 PM   #8
 
Okay, so I did PE = [(9*10^9)(-1.6*10^-19)(1.6*10^-19)] / 5.43*10^-11

My answer is right!!! -4.24 * 10^18

Thank you
Sep23-08, 04:27 PM   #9
 
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Quote by nckaytee View Post
Okay, so I did PE = [(9*10^9)(-1.6*10^-19)(1.6*10^-19)] / 5.43*10^-11

My answer is right!!! -4.24 * 10^18

Thank you
You're welcome.

And don't act so surprised. You had it nailed from kqq/r.

Good luck.
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electric, energy, potential
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