Find the magnitude of the electric field at point P

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Homework Help Overview

The discussion revolves around calculating the magnitude of the electric field at point P due to two identical charged spheres positioned at the vertices of an equilateral triangle. The original poster attempts to apply the formula for electric field strength but expresses uncertainty regarding their calculations and the resulting values.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants explore the application of the electric field formula and question the distance variable used in the calculations. The original poster revisits their approach after realizing a potential error in the distance measurement.

Discussion Status

Some participants have provided feedback on the calculations, and the original poster has acknowledged a mistake regarding the distance used in their initial approach. There is a suggestion that the revised calculations lead to a different answer, which the original poster considers as a possible correct choice.

Contextual Notes

The discussion includes a focus on the correct interpretation of the distance variable in the electric field equation and the implications of using the wrong distance in the calculations. There is an emphasis on ensuring that the reference point is accurately defined in relation to the charges.

paulimerci
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Homework Statement
Question posted below.
Relevant Equations
E = kq/r^2
There are two identical spheres with the same charge that are the vertices of an equilateral triangle. ##+3 \mu C## will exert an outward electric field, which is drawn in the FBD below (see the attached pic), Since the horizontal force components (1x and 2x) are equal and opposite at point P, we can cancel those two vectors, and the remaining y component vectors will give the resultant magnitude of the electric field at point P.
$$ E = \frac {kq}{r^2}$$
$$ E_{1y} = \frac {8.99 \times 10^9 \times 3 \times 10^-6 sin 60} {6.76}$$
$$ E_{1y} = 3455 N/C$$

$$E_{2y} = \frac {8.99 \times 10^9 \times 3 \times 10^-6 sin 60} {6.76}$$
$$ E_{2y} = 3455 N/C$$
$$ E _{net} = 6910 N/C$$
I'm not sure where I made a mistake because none of the answers match my answer. Can anyone point out where my mistake is?
 

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What does r represent in your relevant equation? Think.
 
haruspex said:
What does r represent in your relevant equation? Think.
r is the distance between the charge and the reference point (P).
 
paulimerci said:
r is the distance between the charge and the reference point (P).
I see where I did a mistake I took the wrong distance (between P and the midpoint between two charges). r=3m, Is ##E_{1y} + E_{2y} = 2598+2598 = 5196 N/C##. So the answer choice is B?
 
paulimerci said:
I see where I did a mistake I took the wrong distance (between P and the midpoint between two charges). r=3m, Is ##E_{1y} + E_{2y} = 2598+2598 = 5196 N/C##. So the answer choice is B?
Looks right.
 
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haruspex said:
Looks right.
Thank you!
 

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