# Polarisation on the surface of a sphere

I am trying to answer a question that states:
There is a sphere of radius R centred at the origin with a polarisation P = C(xi+yi+zk), where C is a constant, at the surface. What is the total charge in the sphere if there is no net charge?

I know that P= Nqd where N is the number of charges, q is the charge on each one, and d is the separation distance in the dipoles. But I do not see how to relate this to the sphere in the question. I do not know of any individual charges in the sphere or of any dipoles, or should I be taking these as atoms?
Any pointers in the right direction would be much appreciated.
Thanks.

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siddharth
Homework Helper
Gold Member
I am trying to answer a question that states:
There is a sphere of radius R centred at the origin with a polarisation P = C(xi+yi+zk), where C is a constant, at the surface. What is the total charge in the sphere if there is no net charge?

I know that P= Nqd where N is the number of charges, q is the charge on each one, and d is the separation distance in the dipoles. But I do not see how to relate this to the sphere in the question. I do not know of any individual charges in the sphere or of any dipoles, or should I be taking these as atoms?
Any pointers in the right direction would be much appreciated.
Thanks.
The collection of dipoles leads to formation of bound charges on the surface and within the material.

So, to calculate the total charge, you need to apply Gauss's law for a dielectric.