Electric Fields and charges of equal magnitude

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SUMMARY

In the discussion, two point charges of equal magnitude are positioned 8.4 cm apart, resulting in a combined electric field of 45 N/C at the midpoint. The formula used to calculate the electric field, E = k(q)/r², was applied incorrectly by assuming the distance from one charge to the midpoint rather than considering the contributions from both charges. The correct approach requires calculating the electric field contributions from both charges at the midpoint and setting their sum equal to 45 N/C to find the magnitude of each charge.

PREREQUISITES
  • Understanding of Coulomb's Law and electric fields
  • Familiarity with the formula E = k(q)/r²
  • Knowledge of vector addition in electric fields
  • Basic algebra for solving equations
NEXT STEPS
  • Review the concept of superposition in electric fields
  • Learn how to calculate electric fields from multiple point charges
  • Study the implications of distance in electric field calculations
  • Practice solving problems involving electric fields and point charges
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Students in physics, educators teaching electromagnetism, and anyone interested in understanding electric fields and point charge interactions.

mli273
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1. Two point charges of equal magnitude are 8.4 cm apart. At the midpoint of the line connecting them, their combined electric field has a magnitude of 45 N/C.

Find the magnitude of the charges.



2. E=k(q)/r^2



3. I've tried 45= 8.99x10^9(q)/(.084)^2 and got q to equal 35 pC, but that isn't correct :(
 
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Hi mli273,

mli273 said:
1. Two point charges of equal magnitude are 8.4 cm apart. At the midpoint of the line connecting them, their combined electric field has a magnitude of 45 N/C.

Find the magnitude of the charges.



2. E=k(q)/r^2



3. I've tried 45= 8.99x10^9(q)/(.084)^2 and got q to equal 35 pC, but that isn't correct :(


The quantity 8.99x10^9(q)/(.084)^2 gives the magnitude of the electric field from one charge q at a distance 8.4 cm away from that charge. Do you see why that is wrong for this problem, and what to do now?
 

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