Induced charges concept one charge sitting outside the uncharge sphere

 

You can see that when you keep charge body outside a metallic sphere even though metallic sphere is not charged there is some induced charges so the minus come on one side the Plus is gone the other side so that means there is an electric field created inside right so electric inside the metallic sphere is zero as you know that you know electrostatic shielding we know that is zero as suppose they ask you what is the electric field due to the induced charges then we should know that he induced not he capital he induced is equal to the external charge similarly voltage at the centre can be calculated due to the external charge alone because the induced charges do not contribute for any voltage symmetric + SN -