What is the electric field at a point midway between two charges?

In summary, Coulombs law states that the electric field between two charges is inversely proportional to the distance between the charges.
  • #1
daniel69
10
0
Find the electric field at a point midway between two charges of + 3.0 x 10^-9 C and + 60 x 10^-9 C separated by a distance of 30 cm.


would we utilize coulums law:

[9 x 10^9 * 3.0 x 10^-9 * 60 x 10^-9] / [30/2]
 
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  • #2
daniel69 said:
Find the electric field at a point midway between two charges of + 3.0 x 10^-9 C and + 60 x 10^-9 C separated by a distance of 30 cm.


would we utilize coulums law:

Yes, but this isn't it:
[9 x 10^9 * 3.0 x 10^-9 * 60 x 10^-9] / [30/2]

What is the expression for Coulomb's Law and what do the symbols mean? You need to find the electric field from each of the two charges at a point 15 cm. away from each of them. Keep in mind that electric fields require vectors: which way does the electric field from each charge point at the place midway between the two charges?
 
  • #3
F = k*q1*q2 / r^2

k = contant of 9 x 10^9
q's = the charges
r = the radius or distance

did i forget to square it. is that what i did wrong.
 
  • #4
daniel69 said:
F = k*q1*q2 / r^2

k = contant of 9 x 10^9
q's = the charges
r = the radius or distance

did i forget to square it. is that what i did wrong.

All right -- that's the force equation. The problem is asking for the electric field at a point, so we drop the q2.

Make a picture of the situation. We have a line segment 0.3 meters long (you'll want to work in meters) with a charge on each end. (Are those supposed to be + 3.0 x 10^-9 C and + 6.0 x 10^-9 C ? 60·10^-9 seems rather large compared to the other charge...) Both charges are positive, so which way does the field from each charge point at the position halfway between them? That will tell you whether you want to add or subtract the individual fields.

Now use the formula for the electric field for each charge at the appropriate distance. (How far is the midpoint from each charge?) You then combine the fields appropriately (have you worked with vectors?) to get the total at that midpoint.
 
  • #5
Believe it or not, it should read 60. I had to recheck that myself.

So dropping the q2 should give us:
[k*q1] / r^2

Since both charges are negative, I would guess that they would repel one another and face in opposite directions outward.

I don't know whether to add or subtract the individual fields though.

And half way inbetween would be 30/2 = 15?

I haven't really worked that much with vectors. I know the rules but haven't had much work with application of vectors.

Please help so I can apply this to similar problems.

Thanks
 
Last edited:

1. What is an electric field?

An electric field is a physical quantity that describes the strength and direction of the force experienced by a charged particle in the presence of other charged particles. It is represented by a vector and is measured in units of Newtons per Coulomb (N/C).

2. How is an electric field created?

An electric field is created by any object that has a net electric charge. Positive charges create electric fields that point away from them, while negative charges create electric fields that point toward them. The strength of the electric field also depends on the distance from the charged object.

3. What are the applications of electric fields?

Electric fields have a wide range of applications in our daily lives. Some common examples include the operation of electronic devices, the transmission of electricity through power lines, and the functioning of electric motors. Additionally, electric fields are also used in medical imaging techniques such as MRI scans.

4. How is the strength of an electric field measured?

The strength of an electric field is measured using a device called an electric field meter. This device measures the force experienced by a test charge placed in the electric field and calculates the strength of the field based on this force. The unit of measurement for electric field strength is Newtons per Coulomb (N/C).

5. What is the difference between an electric field and an electric potential?

An electric field and an electric potential are related but distinct concepts. An electric field describes the force experienced by a charged particle, while an electric potential describes the energy that a charged particle has due to its position in an electric field. In other words, the electric field is a measure of the force per unit charge, while the electric potential is a measure of the energy per unit charge.

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