What is the electric field at x=2d?

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Homework Help Overview

The problem involves calculating the electric field at a specific point (x=2d) due to two point charges, q and 2q, located at x=0 and x=3d, respectively. The subject area is electrostatics.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • The original poster attempts to calculate the electric field contributions from both charges and combines them. Some participants question the sign of the resulting electric field and the format required for the answer.

Discussion Status

Participants are exploring the calculations and discussing potential errors in the sign or format of the answer. There is no explicit consensus on the correct answer, but some guidance has been offered regarding the interpretation of signs and formatting requirements.

Contextual Notes

There is mention of specific formatting rules for submitting answers in the online homework system, which may be affecting the original poster's ability to submit their response correctly.

sona1177
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Homework Statement


Positive point charges q and 2q are located at x=0 and x=3d respectively. What is the electric field at x=2d?

Homework Equations



E=kQ/r^2

The Attempt at a Solution


E1=kq/(2d)^2=kq/4d^2
E2=2kq/d^2
E1-E2=7kq/4d^2, to the left

To the left is correct but the answer is wrong :( can someone please tell me why? thanks.
 
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It should be the negative of that. Small mistake but you did everything else correctly.
-7kq/4d^2
 
0ddbio said:
It should be the negative of that. Small mistake but you did everything else correctly.
-7kq/4d^2

When I said left, that was intended to mean the sign was negative. In my online homework, for vectors we can not put in actual signs. For example we have to put it in this format:

magnitude of vector, direction.

that is why i said 7kq/4d^2, to the left--assuming to the right is positive and to the left is negative.

but it's still saying that is wrong :(
 
You're work is right; either the format is wrong, or the program has the wrong solution.

Are you sure you're not supposed to plug in for k or something?
 
What is the answer that you're trying to match?
 

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