# Electric field by charges

A point charge $$Q$$ is placed at a distance $$2R$$ from the centre of a conducting charged spherical shell of radius $$R$$ and having a charge $$Q$$ as shown. The electric potential at point $$P$$ due to charge on shell is $${\dfrac{aQ}{b \pi \epsilon_{o} R}}$$, where $$a$$ and $$b$$ are coprime positive integers. Find $$a+b$$.

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