Charge Q is distributed uniformly over surface of a hemisphere of radius r. Calculate electric field at centre of curvature of hemisphere.
I realise that this should be quite straightforward but I am a bit confused.
The total charge Q is distributed over surface of hemisphere with surface charge density sigma where
sigma = Q/(2*PI*r^2)
I think you would then divide the hemisphere into a series of rings where each ring would carry a charge
At the centre of curvature the components of electric field perpendicular to the axis will cancel so you will only have electric field along the axis z.
Not quite sure where to go from here.