Two point charges

  • Thread starter Mikesgto
  • Start date
  • #1
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Homework Statement


A charge of 0.611 nC is placed at the origin. Another charge of 0.383 nC is placed at x1 = 8.1 cm on the x-axis.
At which point on the x-axis does this potential have a minimum?

Homework Equations


U=(kq1q2)/r


The Attempt at a Solution


I really have no idea how to even start this problem. I've been thinking about it for a couple hours now. Any help would be appreciated.

Homework Statement





Homework Equations





The Attempt at a Solution

 
Last edited:

Answers and Replies

  • #2
rl.bhat
Homework Helper
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Post the complete question.
 
  • #3
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I edited the post. My apologies.
 
  • #4
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And also once I messed up enough the hint was that
"A necessary condition for the potential to have a minimum is that its derivative is 0."

But the derivative of what? The only thing I can think of is the V(r)=kQ/r
 
  • #5
rl.bhat
Homework Helper
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Potential at a point distance x from q1 is given by

V = k*q1/x + k*q2/(d-x) where d is the distance between the charges.

To find the minimum potential between the charge, find dV/dx and equate it to zero.
And find x.
 
  • #6
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Thanks a lot! It was kind of a messy derivative but I am so thankful you helped me out. :)
 

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