Depicted in Figure Q5 is a flat annulus with inner radius a and outer radius b. It is placedin the x-y plane with its central axis aligned with the z-axis. P is a point sited on the z-axis where z is its height above the x-y plane. The flat annulus is uniformly charged with a surface charge density ps. (1) Derive an expression for the voltage V at the point P. (ii) Hence, or otherwise, derive an expression for the electric field E at the point P. (iii) What will be the electric field E when a = 0 and b→ ∞o ?

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