The earth pin of a 3-pin plug is thicker and longer than the live and neutral pins to ensure personal safety until the line and neutral are disconnected.
The larger pin provides less resistance to current flow, allowing more fault current to be passed to the ground on the occurrence of a fault.
The thickness of the earth pin also helps prevent any possibility of mistakenly inserting the earth pin in the wrong pinhole of the socket.
The thickness of the earth pin indicates that any leakage current from an appliance would easily pass through the pin to the ground.
The earth pin should be the first to connect and the last to disconnect with electric supply. This is why earth pin is longer than the live and neutral pin on 3-pin plugins.
When we insert a 3-pin plugin into a 3-pin socket, the earth pin is the first to make contact with the socket as compared to the Live and Neutral Pins.
The earth pin is the last to disconnect from the socket when removing the plug from the socket.
This way, earthing is well maintained during operation for proper safety and protection.