How to Find Electric Fields in a Parallel Plate Capacitor with Two Dielectrics?

[minimark1234]

question:
so here is what my problem is. there are two dielectrics between a parallel plate capacitor. distance between the two plates is '2s' and each dielectric is 's' long. each plate has a charge of $$\itshape \sigma$$ (top being pos. and bottom being neg. and doesn't give an area) how would i go about finding the electric fields in each dielectric.

i was thinking finding the electric field (using a pillbox, and Gaussian theorem) caused by each plate ONLY to the dielectric touching it. after doing that to each do i have to find what the electric field in each dielectric due to the other dielectric and other plate? or am i done there?
it makes sense that i would have to keep going, but then again, i haven't learned enough from my textbook (Griffith EM 2nd edit.) to continue on with the problem. or i might

 

[thebigstar25]

I think I remember the problem you are talking about , (Griffith textbook is a great one but I aslo struggled with the probelms he wrote) ..

anyway, I suggest you start from the fact that : integral of D .da = Q(fenc) ,and find D from there , then you can easily find E using :

D = e E (e here is epsilon) ..

I hope I was able to help you with this problem .. :)

 

[minimark1234]

I think I remember the problem you are talking about , (Griffith textbook is a great one but I aslo struggled with the probelms he wrote) ..

anyway, I suggest you start from the fact that : integral of D .da = Q(fenc) ,and find D from there , then you can easily find E using :

D = e E (e here is epsilon) ..

I hope I was able to help you with this problem .. :)

ok, you that's what i was going for, but do u know if each dielectric is effected by just the plate touching it, or everything including the other dielectric?

 

[thebigstar25]

when you find D you should notice that it is the same for both dielctric, so in order to find E you just need to find (epsilon) for each one then from there you can get E .. Do you agree with that? If it is still not clear ask again ..

 

[minimark1234]

when you find D you should notice that it is the same for both dielctric, so in order to find E you just need to find (epsilon) for each one then from there you can get E .. Do you agree with that? If it is still not clear ask again ..

ya I am pretty sure i get the intuition behind it, ill take it that i just use Gaussian pillbox for each of the dielectrics that it touches and see where that takes me

 

[thebigstar25]

I believe you are starting in the right way, try to solve it and let us know what answer you will end up :) ..