Why Earth pin is longer and thicker in a 3-pin plug?

As we all are familiar with the fact that electricity can be very dangerous when safety is not taken seriously. Our question that “Why Earth pin is longer and thicker in a 3-pin plug?” is primarily related to safety.

Safety must be on top priority when dealing with the electricity. Every electrical appliance with metal bodies must be properly grounded and earthed, because if any live wire touches the metallic body of that appliance, or any leakage current and any short circuit current flows through that metallic body and if someone touches that part, then current will pass through the human body which is highly undesirable in any case.

So to ensure the safety, proper Earthing(Grounding) is needed.

why earth pin is longer and thicker in a 3 pin plug?

We will discuss our topic in two parts as

  1. Why Earth pin is longer?
  2. Why Earth pin is thicker?

Why Earth pin is Longer?

To ensure the proper earthing of that appliance, it is very much necessary that its earth pin should get inserted first and it should be the last one to disconnect from the socket.

By making the earth pin longer than other two pins (phase and neutral) ensures that it will get inserted first and it will also be the last one while disconnecting from socket.

This will ensure that the body of that appliance will always be in connection with the earth (ground), and there will be no risk of safety.

One more reason can be seen now a days because of modern shutter sockets, the shutter of phase and neutral will open only after the opening of earth pin shutter. So, to insert the Earth pin first, it is made longer than other pins.

Why Earth pin is thicker?

We will give two reasons for this question as follows,

  1. To avoid the wrong way to operate a 3-pin plug, like if somebody wants to insert a 3-pin plug upside down or in any other way then it will not fit because earth pin is thicker then other two pins and it can only be inserted in the slot made for earth pin in the socket. This will ensure that the plug will be inserted in the socket in right way always.
Right way to insert 3-pin plug
  1. The second reason for making the earth pin thicker is related to Resistance, let’s discuss it below

Formula for resistance is

                   R= ρl/Ap


R= Resistance

ρ = resistivity

l = length of the conductor

A = area of the crossection

By above formula, we can see that Resistance is inversely proportional to the area of the crossection(thickness) of that conductor. It means that Resistance of the conductor will be less if the thickness of the conductor is more.Low resistance path will allow the current to easily flow through it in any abnormal condition.

I hope that you got the answer that “Why earth pin is made longer and thicker in a 3-pin plug?”

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