Finding electric field through capacitor

[geft]

A parallel-plate capacitor with two dielectrics is placed in a circuit with 10V applied.

Dielectric A has 0.001m width and relative permittivity 2. Dielectric B has 0.003m width and relative permittivity 4. The plates have area of 0.01m^2. What is the electric field through each dielectric? (Ans: 4000 V/m and 2000 V/m)

I know the formula used is E = V/d, but how do I divide the voltage between these dielectrics?

 

[tiny-tim]

hi geft!

I know the formula used is E = V/d, but how do I divide the voltage between these dielectrics?

why would the width matter?

start with the electric displacement field D …

what is its magnitude, and how is E related to it?

 

[geft]

D = eE

E = D/e = V/d

...but I wouldn't be able to get the displacement field without the electric field, right?

 

[tiny-tim]

displacement field was invented for the capacitor …

D = -Q/A ​

 

[geft]

Didn't know that formula, thanks! :)

 

[tiny-tim]

oooh, i forgot to mention …

that's exactly why the electric displacement field D is measured in units of coulombs per square metre, C/m² ​