Outside a uniformly charged sphere the field magnitude at distance r from centre is equivalent to that of

1. Gauss' law gives E·4πr² = q/ε₀ for r > R, so E = q/(4πε₀r²). 2. This is identical to the field of a point charge q at the centre. 3. Hence outside the sphere it behaves like a point charge. _Source: Maharashtra Balbharati Std XII Physics, Ch 8 "Electrostatics" §8.2.1_