Physics: Electricity and Magnetism Question?

Question

pdate : Can someone enlighten me on this question? Thanks! 

Consider three charged sheets, A, B, and C. The sheets are parallel with A above B above C. On each sheet there is a surface charge of uniform density: –4 x 10^(-5) C/m^2 on A, 7 x 10^(-5) C/m^2, on B, and –3 x 10^(-5) C/m^2. (The density given includes charge on both sides of the sheet.) What is the magnitude of the electrical force per unit area on each sheet? Hint: Check to see that the total force per unit area on the three sheets is zero.

Answer 1

Electric field generated by a large (infinite) sheet carrying a uniform surface charge density of s coulombs per meter  is  

We know  =  8.854 187 817... x 10⁻¹² [F/m]

 

Surface charge of uniform density of sheet A is (  )  C/m²

Electrical field per unit area on 1st sheet (E1) =   

= - 2.258 x 

 

Electrical field per unit area on 1st sheet (E1) = -2.258 x  N/C

 

Surface charge of uniform density of sheet B is (  )  C/m²

Electrical field per unit area on 2nd sheet (E2) =  

=  3.953 x 

 

Electrical field per unit area on 1st sheet (E2) =  3.953 x  N/C

 

Surface charge of uniform density of sheet C is (  )  C/m²

Electrical field per unit area on 3rd sheet (E3) = - 

= - 1.694 x 

 

Electrical field per unit area on 1st sheet (E3) = -1.694 x  N/C

Check:

Check whether the total force per unit area on the three sheets is zero.

E1 + E2 + E3 = -2.258 x 10^6 + 3.953 X 10^6 - 1.694 X 10^6 = 0