Electric field and charge density

In summary: You should get a result based on the charges being arranged 1L to 2L, and when measured at 3L, the field will be evaluated with the charges 2L to 3L away.
  • #1
peaceandlove
67
0

Homework Statement


A uniform line charge of density λ lies on the x-axis between x=0 and x=L. Its total charge is 11 nC. The electric field at x=2L is (500 N/C)ˆı. Find the electric field at x=3L. Answer in units of N/C.

Homework Equations





The Attempt at a Solution


I have no clue where to even begin...I know that eventually I need to obtain a relationship between E(2L) and E(3L) but besides that I'm totally lost.
 
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  • #2
peaceandlove said:

Homework Statement


A uniform line charge of density λ lies on the x-axis between x=0 and x=L. Its total charge is 11 nC. The electric field at x=2L is (500 N/C)ˆı. Find the electric field at x=3L. Answer in units of N/C.

Homework Equations



The Attempt at a Solution


I have no clue where to even begin...I know that eventually I need to obtain a relationship between E(2L) and E(3L) but besides that I'm totally lost.

Develop an integral for a charged line segment along the x-axis. Won't that then tell you what the relationship between distance along x and field strength?
 
  • #3
I can't seem to get the integral right... I got (1/4(pi)e_0)*(qQ/(d(d+L)). Perhaps I calculated it wrong because I'm not sure what q is.
 
  • #4
peaceandlove said:
I can't seem to get the integral right... I got (1/4(pi)e_0)*(qQ/(d(d+L)). Perhaps I calculated it wrong because I'm not sure what q is.

What you don't know is what L is.

By giving you the field intensity at 2L, then they are telling you what it is. But rather than calculate it out I'd just go to the ratio and figure the L based on the ratio of the dependency on L.

For instance you should get a result based on the charges being arranged 1L to 2L, and when measured at 3L, the field will be evaluated with the charges 2L to 3L away.
 
  • #5
Do I do that using the integral I developed? And if so does that mean the one I came up with is correct?
 
  • #6
peaceandlove said:
Do I do that using the integral I developed? And if so does that mean the one I came up with is correct?

Sorry, I didn't work out your integral. I simply note that you should have an equation of the form

E = kλ∫ 1/r2 = - K/r

where K is the grouped constants (which will cancel out) and r is evaluated from 1 to 2, or 2 to 3.
Then take the ratio of the equations right?

E3/500 = (K*(1/2 - 1/3))/(K*(1-1/2)
 

Related to Electric field and charge density

1. What is an electric field?

An electric field is a physical quantity that describes the force exerted on a charged particle by other charged particles. It is a vector quantity, meaning it has both magnitude and direction.

2. How is electric field strength calculated?

The strength of an electric field is calculated by dividing the force experienced by a charged particle by the magnitude of the charge. It is measured in units of newtons per coulomb (N/C).

3. What is the relationship between electric field and charge density?

Electric field and charge density are directly proportional to each other. This means that as the charge density increases, the electric field also increases, and vice versa. This relationship is described by the equation E = ρ/ε, where E is the electric field, ρ is the charge density, and ε is the permittivity of the medium.

4. How does the presence of a charged object affect the electric field in its surroundings?

The presence of a charged object creates an electric field in its surroundings. This electric field can either attract or repel other charged objects, depending on their polarity. The strength of the electric field decreases as the distance from the charged object increases.

5. How do conductors and insulators affect the distribution of electric field and charge density?

Conductors have a high concentration of free electrons, which allows them to easily distribute any excess charge and create a uniform electric field. On the other hand, insulators have tightly bound electrons and do not allow for easy distribution of charge, resulting in a non-uniform electric field and higher charge density near the charged object.

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