Neutral Point between point charges

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SUMMARY

The discussion focuses on determining the neutral point between three point charges: Q1 (2nC), Q2 (3nC), and Q3 (-4C). The electric field equations, specifically E = K q / r², are utilized to calculate the electric fields produced by each charge. The participants clarify that the direction of the electric fields must be assigned based on the nature of the charges, with positive charges producing outward fields and negative charges producing inward fields. The final conclusion emphasizes the importance of setting up coordinate axes to accurately determine the resultant electric fields at point P.

PREREQUISITES
  • Understanding of electric fields and their vector nature
  • Familiarity with Coulomb's Law and the equation E = K q / r²
  • Knowledge of charge types: positive and negative
  • Basic skills in vector addition and trigonometry
NEXT STEPS
  • Study vector addition of electric fields in multiple charge systems
  • Learn about electric field diagrams and their interpretations
  • Explore the concept of electric field lines and their significance
  • Review trigonometric applications in physics for vector components
USEFUL FOR

Students studying electromagnetism, physics educators, and anyone interested in understanding electric fields and charge interactions in electrostatics.

Samurai44
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Homework Statement


How can I find the nuetral point between two charges or more ? Example:[/B]
(-Q3)...(0.8m)......(Q2)...(0.3m)...(P)...(0.3m)...(Q1)
Q1=2nC ,,, Q2=3nC,,, Q3=-4C ,,,
q: Determine in which direction must be Q3 moved to make P neutral? Calculate the distance which P will be moved.

Homework Equations


E=K q / r^2

The Attempt at a Solution


what i did i found E of q1 which is 200N/C ,, and q2 = 300N/C
And then stuck...
 
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Electric fields are vector quantities, having both magnitude and direction. So what directions do you assign to the two magnitudes that you've calculated? What's their sum?
 
gneill said:
Electric fields are vector quantities, having both magnitude and direction. So what directions do you assign to the two magnitudes that you've calculated? What's their sum?
Their sum is 100N/C since they are repulsive , No idea about direction XD
 
Samurai44 said:
Their sum is 100N/C since they are repulsive , No idea about direction XD
See if you can find a picture of the electric field surrounding a positive charge, and for a negative charge (your text or the web should have this). What direction are the arrows representing the fields directed in each case?
 
gneill said:
See if you can find a picture of the electric field surrounding a positive charge, and for a negative charge (your text or the web should have this). What direction are the arrows representing the fields directed in each case?
No directions are shown !
 

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Samurai44 said:
No directions are shown !
That's just the problem statement. You're expected to know the directions to assign to the fields produced by positive and negative charges. See if you can find another image showing the fields surrounding charges. I found several in a few seconds by googling "electric field".
 
gneill said:
That's just the problem statement. You're expected to know the directions to assign to the fields produced by positive and negative charges. See if you can find another image showing the fields surrounding charges. I found several in a few seconds by googling "electric field".
ahh i thought you were meaning from the question itself ... XD
definitely for positive its outwards , while negative its inwards
 
Samurai44 said:
ahh i thought you were meaning from the question itself ... XD
definitely for positive its outwards , while negative its inwards
Okay! So now you can assign a direction to the sum of the fields that you calculated earlier, right?
 
gneill said:
Okay! So now you can assign a direction to the sum of the fields that you calculated earlier, right?
well , this is the point I am not getting and need help
What i know is if there's repulsion we subtract , but if there's attraction we add
 
  • #10
At point P sketch in the arrows representing the field direction from the two positive charges (along the line that all the charges lie). Suppose you choose the direction to the right to be the +x-axis direction. Now, those arrows (vectors) have the magnitudes that you calculated previously. What's the resultant of adding them?
 
  • #11
gneill said:
At point P sketch in the arrows representing the field direction from the two positive charges (along the line that all the charges lie). Suppose you choose the direction to the right to be the +x-axis direction. Now, those arrows (vectors) have the magnitudes that you calculated previously. What's the resultant of adding them?
Respecting to P , the direction to right is positive , so E2 - E1 - E3 = 0 ,,, that means E3=E2-E1 which results into 100N/C ...
Now I got the point ! .. So whenever I have two or more charges in a straight line i should make the same concept ?
Thanks a lot
 
  • #12
Samurai44 said:
Respecting to P , the direction to right is positive , so E2 - E1 - E3 = 0 ,,, that means E3=E2-E1 which results into 100N/C ...
Now I got the point ! .. So whenever I have two or more charges in a straight line i should make the same concept ?
Thanks a lot
Yes, that's the idea. You set up coordinate axes and determine both the magnitude and directions of the fields due to each charge before you start adding or subtracting them as the situation warrants. You will find that the same concept applies even if the charges are not along a straight line, in which case you'll deal will all the components of the vectors (time to review your trigonometry!).
 
  • #13
gneill said:
Yes, that's the idea. You set up coordinate axes and determine both the magnitude and directions of the fields due to each charge before you start adding or subtracting them as the situation warrants. You will find that the same concept applies even if the charges are not along a straight line, in which case you'll deal will all the components of the vectors (time to review your trigonometry!).

Alright , Thanks A Lot ! :D
 

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