Final answer:
In charging by induction, the charge induced on a grounded neutral object is opposite to the charge on a nearby charged object. This happens because the neutral object's charges are rearranged, and grounding allows charge to flow to or from the earth to achieve an opposite net charge when the charged rod is removed.
Step-by-step explanation:
In the process of charging by induction, the charge on the neutral object becomes opposite to the charge on the charged object. When a charged rod is brought near a neutral object, such as a metal sphere, the charges within the sphere will rearrange due to electrostatic forces. Negative charges are attracted towards the positively charged rod, leaving the far side of the sphere positively charged if the sphere is initially neutral. If the sphere is then grounded, electrons will flow to or from the ground to neutralize the charge closest to the rod, ultimately leaving the sphere with a net charge that is opposite to the rod's charge upon disconnecting the ground wire before the rod is removed.
For instance, if a positively charged rod is brought near a neutral metal sphere, the sphere's electrons will be attracted towards the rod, leaving the far side of the sphere positively charged. Grounding the sphere allows electrons from the earth to flow into the sphere, neutralizing the positive charge near the rod. When the ground is disconnected and the charged rod is removed, the sphere retains an excess negative charge, which is opposite to the original positive charge on the rod.