There is positive charge inside the hollow conducting sphere, closer to the left edge of the sphere. It attracts more electrons on the left, than on the right.
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What I can't get is why is the charge distribution on the outer surface uniform, even if negative charge on the inner surface is not uniform due to the off-centred electric charge placed inside the cavity?
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The field outside of the sphere will be induced by charge $+q$. Will this field be induced by the positive charge on the outer surface, or by the charge inside the sphere?
Best Answer
The superposition principle allows for solution construction from different pieces. The first piece of the solution in this problem, it is a system of a $+q$ point charge and $-q$ inner surface charge which induces zero electric fields outside the inner surface. The electric field in the volume of metal is zero. From Newtonian times it is known, that uniform distribution of charges (masses) gives zero electric (gravitational) field inside a sphere. Hence, the second piece of the solution is the uniform $+q$ charge distribution on the outer surface. And from this solution, it follows that the electric field outside the outer surface is that of the uniformly distributed over the outer sphere $+q$ charge.