Worked example: A neutral aluminium sphere X on an insulating stand is charged by induction using a negatively charged rod, following the earthing method. (a) What is the final sign of charge on X? (b) What happens if the steps are done in the wrong order — the rod is removed before disconnecting the earth wire? Step 1: The negative rod repels free electrons in X to the far side, making the near side positive and far side negative. Step 2: Earthing the far side lets the repelled electrons escape to the ground, leaving X with a deficit of electrons (positive) on the near side, which spreads over the whole sphere. Step 3: Disconnect earth, then remove rod: X is left positively charged — opposite to the inducing rod. (b) If the rod is removed first, the polarization disappears; electrons from the ground flow back or the excess drains, and X ends up neutral again — the charging fails. This shows why the correct sequence (earth off first, rod second) is essential.