Finding electric field between two charges

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Homework Help Overview

The discussion revolves around calculating the electric field magnitude between two point charges, Q1 and Q2, which are positioned a specific distance apart. The original poster presents their calculations and seeks validation of their approach.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to calculate the electric field by determining the contributions from each charge at a midpoint and then combining these values. Some participants question the accuracy of the calculations and suggest verifying the reasoning behind the physics involved.

Discussion Status

Participants are engaging in a review of the calculations presented, with some offering affirmations and others encouraging the original poster to independently verify their work. There is an emphasis on understanding the underlying principles rather than solely relying on confirmation from peers.

Contextual Notes

Participants note that rounding during calculations may lead to variations in the final answer, and they highlight the importance of checking both numerical substitutions and the physical reasoning behind the problem.

joel amos
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Homework Statement


Two charges, Q1 = 4*10-8 and Q2 = 2.7*10-8 are 3.25 m apart.
What is the electric field magnitude halfway between them?

Homework Equations


E = kQ/r2

The Attempt at a Solution


E1= k (4*10-8C)/(1.63m)2
= 135 N/C
E2= k (2.7*10-8C)/(1.63m)2
= 91.4 N/C

135 N/C - 91.4 N/C = 43.5 N/C

Is this correct?
 
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Yes. You will get somewhat different answers depending on how you round your numbers during the calculation.
 
Looks ok. Do you have a reason to doubt it?
 
It is best you don't rely on someone else to tell you if you are right or not.
Take this opportunity to practice :)

There are only two ways you are likely to be wrong in this problem:
1. you got the numbers wrong
2. you got the physics wrong

for 1 you just check your substitution
for 2 you go through your reasoning to see if your answer is consistent with the way charges behave.
When you start out doing this stuff it seems quite hard but you'll quickly get used to it.
 

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