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There is a sphere of radius R centred at the origin with a polarisation

**P**= C(x

**i**+y

**i**+z

**k**), 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.