Find the Electric Field at a midway point

AI Thread Summary
To find the electric field at the midpoint between two charges of +30.0 x 10^-9 C and +60.0 x 10^-9 C separated by 30 cm, the correct approach involves calculating the electric field contributions from both charges. The initial calculations yielded 3000 N/C from the first charge and 6000 N/C from the second, leading to a total of 9000 N/C, which was identified as incorrect. The correct method requires recognizing that the fields from both charges add together, but their directions must be considered, as they point away from the positive charges. The midpoint is 15 cm (0.15 m) from each charge, not 0.3 m, which is crucial for accurate calculations. Ultimately, understanding the direction of the electric fields and the correct distance is essential for solving the problem accurately.
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The problem is:
Find the electric field at a point midway between two charges of +30.0 x 10^-9C and +60.0 x 10^-9 C separated by a distance of 30 cm.


I used E=k (Q/r^2)
My attempt is:

E=(9x10^9)(30.0 x 10^-9C)/(.3m^2)
E=3000 N/C

E=(9x10^9)(60.0 x 10^-9 C)/(.3m^2)
E=6000 N/C

added they are 9000 N/C. I am fairly certain this is incorrect, but I do not understand the material. I really have no idea why or how to go about finding the correct answer. Please help!
 
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I think you might want to try subtracting them like 6000-3000=3000.
I think that electric fields go away from positive charges
 
I still don't really understand. Is .3m really the right radius? It's the distance between the charges, but I'm not sure if it's the right radius to use. Any suggestions? :/
 
Always draw a diagram. If the two charges are separated by 30 cm, how far is the mid point from each charge? Pay attention to the directions of the fields that each charge produces at the given location.

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Thank you so so so much! that was so helpful! I think I solved it correctly now. :) thanks so much!
 
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