Two Point Charges Net Electric Field

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Homework Help Overview

The problem involves calculating the net electric field at specific points due to two point charges located on the x-axis: a negative charge at the origin and a positive charge at x = 10.0 cm. Participants are attempting to determine the electric field at points x = +4 cm and x = -4 cm.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the application of the electric field formula and the impact of charge signs on the net electric field. There are attempts to calculate the electric fields at the specified points, with some questioning the correctness of their calculations and the approach of using absolute values for charges.

Discussion Status

The discussion is ongoing, with participants expressing uncertainty about their calculations and the correctness of their answers. Some guidance has been offered regarding the qualitative addition of electric fields, but there is no clear consensus on the correct approach or final answers.

Contextual Notes

Participants are constrained by the requirement to submit specific numerical answers online, which adds pressure to ensure accuracy in their calculations. There is also mention of the need to consider significant figures in their final answers.

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Homework Statement



Two point charges lie on the x axis. A charge of -2.5 µC is at the origin, and a charge of +8.5 µC is at x = 10.0 cm.

What is the net electrical field at points x = +4 and at x = -4?

Homework Equations



E = kq/r^2

The Attempt at a Solution



For x = +4...

E= 9x10^9(8.5x10^-6)/.06^2 = 21250000
E= 9x10^9(-2.5x10^-6)/.04^2 = -14062500

Net E = 7187500 (which is wrong)

How do I solve this? Thanks.
 
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use absolute values for charges and then add/subtract them up qualitatively.

the -2.5uC will make the E field LARGER at point x=+4 so you would add it instead of subtract.
 
That didn't work.
 
I'm pretty sure it should work. What's the correct answer for both positions?
 
It doesn't give me the right answer until I submit the right answer. I entered 35312500 for x = +4 and it says that is incorrect. (I submit the answers online)
 
the answer is 3.5*10^7 after sig figs.
 
theRIAA said:
the answer is 3.5*10^7 after sig figs.

It says that is wrong too
 

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