UPSC NDA I 2022 General Ability Solved Paper

Concept:For a positively charged conducting sphere, the charge resides on its surface, making the sphere an equipotential surface.The electric field lines must be perpendicular to any conductor's surface at equilibrium.Since the charge is positive, the field lines point radially outward from the centre.Explanation:Consider an isolated conducting sphere with total positive charge $+Q$.All excess charge lies on the outer surface due to repulsion among like charges.Inside the conductor, the net electric field is zero ($E = 0$).Gauss's law confirms this: for any closed surface inside the conductor, the enclosed charge is zero, so electric flux $\Phi = 0$.At the surface, the electric field must be perpendicular to the surface; otherwise, the tangential component would cause charge motion, contradicting equilibrium.For a sphere, "perpendicular to the surface" means along the radial direction.Since the charge is positive, the field points outward, away from the centre.Thus, the field lines are at right angles to the conducting surface and directed radially outward.Answer:Option D: at right angles to the conducting surface and outwards from the centre of the sphere.