Why is Earth Pin Thicker and Longer than Others on 3-Pin Plug?

The electrical devices with metal bodies should be properly earthed and grounded.

In any case, the Phase/Hot/Live/Line wire touches the device metallic body, or in case of short or leakage current inside the appliance, and a person touches the device, mains current will flow through the person's body to the earth and get an electric shock (it a chance to kill).

To avoid that an earthing is provided.

It has a low resistance path to this leakage current for this alow resistance conductor usually copper connected to the metal body and grounded properly.

So, whenever a person is in contact with an electrical appliance having fault, as compared to the human body resistance of the earthing wire is very low and the current goes through the earth wire and not from the human body.

You may notice the Earth Pin on a 3-Pin Plug is thicker and longer other than Line (Phase) and Neutral Pin, but why? - The answer is here.

Reasons for Thicker Earth pin

Safety purpose. The earth pin is thicker and bigger to prevent the wrong way to operate a 3-pin plug.

It can not be inserted (or fit) in the live and neutral slot of the socket even by mistake.

Low resistance. As we know that the resistance is inversely proportional to the area of the conductor.

Therefore, the thicker conductor lesser is the resistance and the electric current always finds the easiest way (having very low resistance) to complete the path.

The law of resistance is, R = ρ (L/a)
[Where: R = Resistance; ρ = Resistivity; L = Length of the Conductor; a = Area of the conductor]

Reasons for Longer Earth pin

Operate safety Shutter. Now, the modern 3 pin wall sockets have a safety shutter on the Line and Neural slots.

It is in-build to prevent someone (especially children) to insert conducting materials in it which causes an electric shock.

The longer earth pin help to open the shutters for Line and Neutral pins i.e. without a longer earth pin, The shutters for Line and Neutral remains closed for better safety.

Connect and Disconnect. The earth pin is longer than the live and neutral pin on the 3-pin plugin.

When we insert a 3-pin plugin into a 3-pin socket, the earth pin is the first to make a contact with the socket as compared to the Live and Neutral Pins and discharge the electrical potential through the ground.