Equipotential Contours and Point Charge

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SUMMARY

This discussion focuses on calculating the charge of a point charge at the origin using equipotential contours. The correct approach involves using the equation V = kQ/R, where V is the voltage, k is Coulomb's constant (8.99e9 Nm²/C²), and R is the radius of the contour. Participants emphasize that the radius can be directly measured from the graph, negating the need for the Pythagorean theorem. The correct calculation method is crucial for solving the problem accurately, especially under time constraints.

PREREQUISITES
  • Understanding of equipotential contours
  • Familiarity with Coulomb's law and the equation V = kQ/R
  • Basic knowledge of voltage and charge relationships
  • Ability to interpret graphical representations of electric fields
NEXT STEPS
  • Study the concept of equipotential surfaces in electrostatics
  • Learn how to accurately measure radius from graphical data
  • Review Coulomb's law and its applications in electric fields
  • Practice problems involving point charges and equipotential contours
USEFUL FOR

Students studying electrostatics, physics educators, and anyone preparing for exams involving electric fields and potential calculations.

GingerBread27
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We haven't really covered this in class so I need some help.

Assuming that these contours are those of a point charge at the origin, calculate the value of the charge in C.

I tried using the equation kQ/R but that's wrong, I'm not even sure I'm using it right in fact. Any help? Thanks
 

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your equation is completely fine... check your number... Maybe your calculator needs a new battery... :-p
 
My calculator is just fine thanks, but I'm still getting it wrong. I'm using -7500 V as Q and then figuring out the radius by using the pythagoream theaorem, still getting it wrong. Help
 
Why are you using pythagorean theorem? Each contour is a circle... you can measure R right off the graph... You can use any contour, but I'd use the one at R=1m.
 
Well both the x and y-axis measure distance so i thought i'd have to find the radius of the circle by using the pythagoream theorem. Even by using r=1m i still get it wrong. :mad:
 
write your number out and let us check for you...
warning: what is the sign of charge?
 
kQ/r=[(8.99e9 Nm^2/C^2)*(-7500 V)]/sqrt(.8^2+1.0^2)=-5.265e13. Is this completely wrong lol. We haven't covered it in class, and incidentally the homework is due tomorrow (my only problem left!), and our book seriously does not help.
 
V=kQ/r
V is the voltage, and Q is the unknown charge you need to find...You mess up these two numbers
you don't need the pythagoream therom to get the r, look carefully, the radii of the circle is same as the number @ x-axis
 

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