A point charge +12μC is placed at the centre of a thin charged metallic shell of radius 10 cm. It charge on the shell is −2μC, intensity of electric field at a distance 30 cm from the centre of the shell is

Consider a spherical Gaussian surface of radius 30 cm with its centre at the location of +9μc charge∴ Qnet=(12−2)μC=10μCBy Gauss's law, Qnet=∈0.ϕE⇒Qnet=∈0.E.4πr2∴ E=14π∈0Qnetr2=9×109×10×10−6/(0.3)2 NC=106 NC