Electric field, surface charge density

In summary, the conversation discusses an expression for Vab and how it relates to ΔV=-∫E dl. The speaker is unsure of how the expression was found and asks for an explanation. Another person suggests using Gauss' law for D to obtain an explicit expression for D in terms of the free charge Q.
  • #1
Cocoleia
295
4

Homework Statement


upload_2017-2-26_12-51-39.png


Homework Equations

The Attempt at a Solution


I have the full solution, the first part being:
upload_2017-2-26_12-52-38.png

I don't understand how they came up with the expression for Vab. I know usually ΔV=-∫E dl, but I'm not sure how they found their expression. Can someone explain? Thanks.
 
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  • #2
Cocoleia said:
I know usually ΔV=-∫E dl, but I'm not sure how they found their expression.
Yes, you can think of their expression as coming from ΔV=-∫E dl if you express E in terms of D. Use Gauss' law for D to obtain an explicit expression for D in terms of the free charge Q on the inner conductor.
 

FAQ: Electric field, surface charge density

1. What is an electric field?

An electric field is a physical quantity that describes the influence of electric charges on each other. It is a vector field, meaning it has both magnitude and direction, and it is created by the presence of electric charges.

2. How is electric field strength measured?

Electric field strength is measured in units of volts per meter (V/m). It can be measured using a device called an electric field meter, which detects the force exerted on a charged object placed in the field.

3. What is surface charge density?

Surface charge density is a measure of the amount of electric charge per unit area on the surface of a conductor. It is represented by the symbol σ and is measured in units of coulombs per square meter (C/m^2).

4. How does surface charge density affect the electric field?

Surface charge density has a direct relationship with the electric field. The higher the surface charge density, the stronger the electric field will be at that point. This is because the electric field is created by the presence of electric charges, and a higher surface charge density means there are more charges in a given area.

5. What is the difference between electric field and surface charge density?

Electric field and surface charge density are related but different concepts. Electric field is a physical quantity that describes the influence of electric charges on each other, while surface charge density is a measure of the amount of electric charge per unit area on the surface of a conductor. In other words, the electric field is the cause of the surface charge density, and the surface charge density is the effect of the electric field.

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