# Electric Field: Find Distance z Above Line Segment

• leonne
In summary, the conversation discusses finding the electric field at a distance z above one end of a straight line segment of length L, which carries a uniform charge. The conversation references the formula de=1/4pie Eo (Q/r^2), and discusses how to calculate the components of the electric field using cos and sin, or simply finding the magnitude without using cos and sin. There is also mention of different solutions being found for the problem.
leonne

## Homework Statement

Find the electric field distance z above one end of the straight line segment of length L which carrys uniform charge

## Homework Equations

de=1/4pie Eo (Q/r^2) r^

## The Attempt at a Solution

This was an example in a book and have few questions about it what they did was

using that formula de=1/4pie Eo (dQ/r^2) cos@
then plugs in, de=1/4pie Eo (y dx/(z^2+x^2) ) (z/(z^2+x^2)^1/2 y is the uniform charge.
My question is why did they do this as in how did they figure out r^2= (z^2+x^2) that dq= ydx and that r^ = cos@

I am bad at setting up the physics problem, i have no problem after everything is set up to solve it.
Thanks

hi leon

since you are trying to find the electric field at one end of the rod, you don't need to use
$\cos{\theta}$ in the formula. since you are presenting the solution from the book,are you sure they are finding the electric field at one end and not at the center of the
rod ? if author is trying to find the electric field at the center of the rod, distance z above it,
then having $\cos{\theta}$ there makes sense , since in that case we only count
the component of the electric field away from the rod...

Hey well actually it was a problem and found the solution on crampster, but after looking at the solution in the solution manual they have different answer, but they both use the cos ( maybe on crampster they simplified the final answer or something looks like they solved it same way)
well here's the step by step on what they did (idk if u have an account or not)
http://www.cramster.com/solution/solution/178791

Last edited by a moderator:
hi

i see what's happening... i did calculation for the magnitude of E and they are doing calculations for the horizontal and vertical component of the E.. while calculating the components you will need to use cos and sin...but if you are just interested in the magnitude then you can do like I say...

o ok thxs

good luck

## 1. What is an electric field?

An electric field is a physical quantity that describes the strength and direction of the force exerted by electric charges on other electric charges. It is represented by vector arrows and is measured in units of volts per meter (V/m).

## 2. How is the electric field above a line segment calculated?

The electric field above a line segment is calculated using the equation E = kQz / (z^2 + r^2)^(3/2), where k is the Coulomb's constant, Q is the charge of the line segment, z is the distance above the line segment, and r is the length of the line segment. This equation takes into account the shape and size of the line segment to determine the electric field at a specific distance above it.

## 3. What is the significance of finding the distance above a line segment in the electric field?

Finding the distance above a line segment in the electric field is important because it allows us to understand the strength and direction of the electric field at a specific point. This information is crucial for many applications, such as designing electronic circuits and determining the behavior of charged particles in an electric field.

## 4. Can the electric field above a line segment be negative?

Yes, the electric field above a line segment can be negative. This indicates that the direction of the electric field is opposite to the direction of the positive charge on the line segment. Negative electric fields are commonly observed when there are multiple charges present, causing the electric field to cancel out in certain areas.

## 5. How does the distance above a line segment affect the strength of the electric field?

The distance above a line segment has a direct impact on the strength of the electric field. As the distance increases, the electric field decreases according to the inverse square law. This means that the electric field is inversely proportional to the square of the distance from the line segment. Therefore, the farther away from the line segment, the weaker the electric field will be.

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