What is the Strength of the Electric Field?

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Homework Help Overview

The discussion revolves around determining the strength of the electric field at a specific distance, r = 7.3 cm, using the formula related to dipole moments. Participants are exploring the implications of the dipole moment and the constants involved in Coulomb's law.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants are attempting to apply the formula for the electric field strength but are questioning the use of charge versus dipole moment in their calculations. There is also a discussion about the relationship between the dipole length and the distance r.

Discussion Status

Some participants have provided insights into potential misapplications of the formula, particularly regarding the dipole moment. Others are seeking clarification on the complete problem statement and the assumptions being made about the geometry of the setup.

Contextual Notes

There is a mention of the figure referenced in the problem, which indicates a separation of charges and suggests that a = r, prompting further exploration of the problem's parameters.

littlejon
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Homework Statement


Specify the strength of the electric field. Let r = 7.3cm .

Homework Equations


E1= (k*p)/(r^2+a^2)^3/2
Here k= constant used in Coulomb's law. a= half the length of dipole
p= dipole moment = charge x length of dipole. Charge = 3nC and length of dipole

The Attempt at a Solution


E1= (9E9)(3E-9)/(.146)^2+(.073)^2)^(3/2)= 6207

I got this wrong, but does anyone have any advice on how to solve this?
 

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littlejon said:

Homework Statement


Specify the strength of the electric field. Let r = 7.3cm .

Homework Equations


E1= (k*p)/(r^2+a^2)^3/2
Here k= constant used in Coulomb's law. a= half the length of dipole
p= dipole moment = charge x length of dipole. Charge = 3nC and length of dipole

The Attempt at a Solution


E1= (9E9)(3E-9)/(.146)^2+(.073)^2)^(3/2)= 6207

I got this wrong, but does anyone have any advice on how to solve this?
It appears that you used the amount of charge for p, rather than dipole moment.

## p=2aq ##
 
SammyS said:
It appears that you used the amount of charge for p, rather than dipole moment.

## p=2aq ##
Then ((9E9)(2*.073*3E-9))/((.146^2)+(.073)^2)^(3/2) = 906?
 
I'm surprised that a problem like this would have a be larger than r. Usually it's the other way around.

What is the complete problem you were given to solve? -- word for word.
 
SammyS said:
I'm surprised that a problem like this would have a be larger than r. Usually it's the other way around.

What is the complete problem you were given to solve? -- word for word.
What are the strength and direction of the electric field at the position indicated by the dot in the figure (Figure 1) ?
Specify the strength of the electric field. Let r = 7.3cm .
Express your answer using two significant figures.
Thats word for word.
 
littlejon said:
What are the strength and direction of the electric field at the position indicated by the dot in the figure (Figure 1) ?
Specify the strength of the electric field. Let r = 7.3cm .
Express your answer using two significant figures.
That's word for word.
In the figure, the charges have a separation, 2r . That is to say, a = r .

physics-problem-png.80347.png
 

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