Question:What is the magnitude of the electric field at point A which is a distance x above the point P? The line AP is perpendicular to the plane of the ring. Express your answer in terms of the following variables, if necessary, R1, R2, σ, x and the constant ϵ0 (if needed, enter pi for π, epsilon_0 for ϵ0, sigma for σ, R_1 for R1 .. etc).

My answer: (x*(2*pi*sigma*R_1*(R_2-R_1)))/((4*pi*epsilon_0*(R_1^2+x^2)^(3/2)))

Which is wrong. Not understanding why. Only looking for help here, not an answer to this. Can someone point me in the right direction to make a proper equation? Please?

Question

Question:What is the magnitude of the electric field at point A which is a distance x above the point P? The line AP is perpendicular to the plane of the ring. Express your answer in terms of the following variables, if necessary, R1, R2, σ, x and the constant ϵ0 (if needed, enter pi for π, epsilon_0 for ϵ0, sigma for σ, R_1 for R1 .. etc).


My answer: (x*(2*pi*sigma*R_1*(R_2-R_1)))/((4*pi*epsilon_0*(R_1^2+x^2)^(3/2)))

Which is wrong. Not understanding why. Only looking for help here, not an answer to this. Can someone point me in the right direction to make a proper equation? Please?

turingtest · Answer

do you have the formula for the E field at that point due to an infinitely thin ring yet?

turingtest · Answer

I can't help if you don't talk to me

turingtest · Answer

do you understand the problem with the infinitely thin ring? that is a precursor to understanding this one

anonymous · Answer

Maybe not.....clearly not. I was just looking over my text book again before answering your question.

turingtest · Answer

If you don't understand the problem about the ring (2nd prob) then you won't understand the one about the disk. To start from how to do the ring problem will take at least an hour to explain, which I don't really have right now. I will be back in about 4 hours; then I can help you in detail.

turingtest · Answer

don't be sorry, this is a cool problem :)
did you get question 2 right though? because if you did, then 3(b) is not that hard

turingtest · Answer

if you got 2b correct, 3b is pretty straightforward

anonymous · Answer

I did get 2. 
1/(4*pi*epsilon_0)*(x*Q)/(x^2+R^2)^(3/2)

turingtest · Answer

ok, great, so what do you have for $d\vec E$ for the disk problem?
what will be your new $dQ$ ? (that is the only part that will change)

anonymous · Answer

wrong as it may be...and i don't know why.....(x*(2*pi*sigma*R_1*(R_2-R_1)))/((4*pi*epsilon_0*(R_1^2+x^2)^(3/2)))

turingtest · Answer

an element of charge on a line segment is $dq=\lambda d\ell$. you need to review the different ways to represent charge differentials for a line, surface, or volume. it's all in the textbook. look it over, and I'll see you later. welcome!