# Electromagnetics coulombs law and field intensity

Alwaysprolol

## Homework Statement

The circular region, ρ < a, z= 0, carries a uniform surface charge density ρ ( subscript s). Find E at P(0,0,h), h > 0.

## Homework Equations

Coulombs law
Field of a line charge and field of a sheet charge.

## The Attempt at a Solution

I'm not sure what they are asking for , but my attempt I used the equation for a field of a sheet of charge cause it's the only one provided in the Homework that contains the ρ (subscript s).

It says E at point (0,0,h) so I'm guessing since its at z = 0 then the vector would be (0,0,h-0). Resulting in my result of

E = (ρ(subscript s) / 2ε ) (0,0,h)

Im not really sure what I'm supposed to be finding

Alwaysprolol
Okay so I get a little bit, I'm looking for the E of a circular region with the radius of ρ ?

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## Homework Statement

The circular region, ρ < a, z= 0, carries a uniform surface charge density ρ ( subscript s). Find E at P(0,0,h), h > 0.

## Homework Equations

Coulombs law
Field of a line charge and field of a sheet charge.

## The Attempt at a Solution

I'm not sure what they are asking for , but my attempt I used the equation for a field of a sheet of charge cause it's the only one provided in the Homework that contains the ρ (subscript s).

It says E at point (0,0,h) so I'm guessing since its at z = 0 then the vector would be (0,0,h-0). Resulting in my result of

E = (ρ(subscript s) / 2ε ) (0,0,h)

I'm not really sure what I'm supposed to be finding
Hello Alwaysprolol. Welcome to PF !

(Use the X2 and X2 icons for superscripts & subscripts.)

Using the E field for an infinite sheet gives the wrong answer.

Do you have an expression for the E field along the axis of a ring of charge?

Alwaysprolol
Hello Alwaysprolol. Welcome to PF !

(Use the X2 and X2 icons for superscripts & subscripts.)

Using the E field for an infinite sheet gives the wrong answer.

Do you have an expression for the E field along the axis of a ring of charge?

Thanks!

Unfortunately, I was not given one. The professor has given us only equations for E of a line charge and a sheet and I'm not quite sure how to utilize them in this question since its asking for the E in a circular region