Guass's law nonconducting plates

[jimbo71]

Homework Statement

Two very large, nonconducting plastic sheets, each 10.0 cm thick, carry uniform charge densities \sigma_{1}, \sigma_{2}, \sigma_{3}, and \sigma_{4} on their surfaces, as shown in the figure . These surface charge densities have the values sigma_{1}= -6.00microC/m^{2}, \sigma_{2}= +5.00 micro C}/m}^{2}, sigma_{3}= +2.00 micro C}/m}^{2}, and \sigma_{4}= +4.00 micro C}/m}^{2}.

1.Use Gauss's law to find the magnitude of the electric field at the point A, 5.00 cm from the left face of the left-hand sheet.

2.Find the direction of the electric field at the point A.

3.Find the magnitude of the electric field at the point B, 1.25 cm} from the inner surface of the right-hand sheet.

4.Find the direction of the electric field at the point B.

5.Find the magnitude of the electric field at the point C, in the middle of the right-hand sheet.

6.Find the direction of the electric field at the point C.

Homework Equations

E=(1/4*pi*epsilonnaut)(q/R^2)

The Attempt at a Solution

I'm not really sure how to set this problem up. I'm not sure if all the charges act on each point

 

[Doc Al]

Homework Equations

E=(1/4*pi*epsilonnaut)(q/R^2)

That's the field from a point charge--you won't need that for this problem.

The Attempt at a Solution

I'm not really sure how to set this problem up. I'm not sure if all the charges act on each point

Use Gauss's law to find the field from a sheet of charge. Then add up all the fields at each point in question.

 

[carlee172]

I know we have to use E=sigma/2epsilon, but I'm not sure which fields (1 and/or 2 and/or 3 and/or 4) to add together for point A for example.

 

[Doc Al]

They all count--add them all. (Be careful with their direction and sign.)