Solve Electric Field: Find q Given E, k, and r

AI Thread Summary
The electric field between two equal but opposite point charges is given as 894 N/C, with a distance of 17.2 cm between them. To find the magnitude of the charge, the formula E = k*q/r^2 is used, where r is the distance from the charge to the midpoint. The correct distance to use for calculations is 0.086 m, not halving the electric field value. Participants emphasize the importance of correctly applying the electric field formula based on the distance from each charge. Understanding the setup of the equation is crucial for solving the problem accurately.
matt.
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Homework Statement



The electric field midway between two equal but opposite point charges is 894 N/C, and the distance between the charges is 17.2 cm. What is the magnitude of the charge on each?

Homework Equations



E = Fe/q

Fe = kq1q2/r^2

The Attempt at a Solution

Electric field = k*q/r^2 = 447 N/C. You know r and k, so just solve for q.

I tried about 5 times already and it is always wrong my most recent attempt I divided the Electric Field by two so I had 446 N/C = 8.99e9 * q/.172^2. But it was wrong.

I might have typed this up wrong but I am new here, sorry. If you guys could help me that'd be great. Thank you.
 
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Hi matt, welcome to PF.
You are finding the field at the midpoint of the two charges. Then what is r?
 
rl.bhat said:
Hi matt, welcome to PF.
You are finding the field at the midpoint of the two charges. Then what is r?

0.086 m?

Then how would I set that up? Is the Electric Field also divided by 2?
 
No. The electric field has it's formula as a function of the distance of each charge.

Do you know how to write the expression for the electric field at some point on the line connecting the charges? (name the distance from one charge x)
 

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