Calculate the ratio q1/q2 of the two charges

  • Thread starter Thread starter simplicity12
  • Start date Start date
  • Tags Tags
    Charges Ratio
Click For Summary
SUMMARY

The discussion focuses on calculating the ratio of two electric charges, q1 and q2, given their distances from point A and the condition that the electric potential at A is zero. The user initially calculated the ratio as q1/q2 = 0.40 but failed to account for the sign of the charges. The correct approach involves recognizing that one charge must be negative to ensure the potentials cancel each other out at point A. The final equation is established as V_A = V_1 + V_2 = 0, leading to the conclusion that V_1 = -V_2.

PREREQUISITES
  • Understanding of electric potential and its calculation using the formula V = kq/r
  • Knowledge of scalar quantities in physics, particularly in the context of electric potential
  • Familiarity with the concept of charge polarity and its effect on electric potential
  • Basic algebra skills for manipulating equations
NEXT STEPS
  • Study the principles of electric potential and charge interactions in electrostatics
  • Learn about the concept of superposition in electric fields and potentials
  • Explore the implications of charge polarity on electric potential calculations
  • Review problem-solving techniques for electrostatic scenarios involving multiple charges
USEFUL FOR

Students studying physics, particularly those focusing on electrostatics, as well as educators seeking to clarify concepts related to electric potential and charge interactions.

simplicity12
Messages
27
Reaction score
0

Homework Statement


Charge q1 is 0.16 m from point A. Charge q2 is 0.40 m from point A. The electric potential at A is zero. Calculate the ratio q1/q2 of the two charges.


Homework Equations


V= kq/r


The Attempt at a Solution


I did
kq1/r1 = kq2/r2
q1/q2 = r1/r2
q1/q2 = 0.16/0.40
q1/q2 = 0.40
My magnitude is right, but the answer is a negative, -0.40. What am i doing wrong?
 
Physics news on Phys.org
You need the potentials to cancel out at A. Since potential is a scalar, you want the potential from one to be positive at A, ad the potential from the other at A to be the negative of the first at A, so they will add to zero. So, assume one charge is negative and put the negative sign in there. That is why your sign is off.

Your initial equation should read:

\frac{KQ_1}{r_1}=-\frac{KQ_2}{r_2}Does this help?
 
So does that mean that my initial equation is:
Vt=V1 + V2? So that when i make the Vt=0, the equation will read V1=-V2?
 
Yes,
V_A = V_1+V_2

But we want the potential at A equal to zero so:

V_A = V_1+V_2=0

V_1=-V_2
 
that helps a lot! thank you very much! :D
 
No Problem!
 

Similar threads

  • · Replies 2 ·
Replies
2
Views
1K
Replies
2
Views
1K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 10 ·
Replies
10
Views
3K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 5 ·
Replies
5
Views
4K
Replies
2
Views
2K
  • · Replies 1 ·
Replies
1
Views
3K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K