Why Earth Pin Longer and thicker than Others Live or Neutral Pin in a Three Pin Plug?

Why Earth Pin Longer and thicker than Others Live or Neutral Pin in a Three Pin Plug?

Does 3 pin Plug provided for better safety and prevent electrocution or protection no longer required?


Have a look! The earth pin of a three pin plug is heavier (longer and thicker) than others two phase and neutral! But, we know earthing or grounding wire do not carry continuous current, where phase wires do. Do you realized? Why this guy is heavier? If not, lets research.

The earth pin on a plug is longer than the live and neutral pins means ensure the earth pin is the first to connect and the last to disconnect.

Earthing is the process of connecting a reference point of the electrical system to the earth for safety reasons where an Earth pin is provided to the switch to pass the leakage currents to the earth at zero potential.

Earthing Pin Length makes more protected the equipment. Lets more details this in a very simple manner.

If the earthing pin is longer then phase and neutral pin then  plugin time earth will connect first then phase & neutral and unplug-in time the phase & neutral will disconnect before the earth. 

So we can say that the equipment is first earthed and then is given the supply and similarly disconnect the supply then remove the earth that provides the equipment more protection.



Thicker the earth pin than others helps the earth pin to being larger cross sectional area of the earth pin. Larger the cross section of any conductor lesser the resistance or easy path to flow the earthing current. 

So the resistance of the earth pin will be least of the three pins. We know the formula R=(ρL)/A where r= resistance, rowρ = resistivity, L=length A=area.

Hence resistance inversely proportional to area so more the area less the resistance and the fault current passes through low resistance path and equipment are  safe.
How Calculate Conductor Resistivity?

What happen if all pins are same sized?

Now consider all three pins of the three pin plug are of same size and diameter. If you know which pin is live, which pin is ground and neutral then it is fine and you can insert plug exactly whatever in the socket., but in practical that very difficult to keep in mind all time.

But, if you don't know pins role and your wrong plugin and touched the metallic part of electric device’s body; you will definitely get an electric shock.



Why is the Earth pin of some 3-pin plugs made of plastic?

There are double insulated electrical appliances which only require two connections - a line (phase) and a neutral to the supply. A double insulated appliance is designed in such a way that it does not require an earth connection for safety. In this case, the protection against electric shock is usually achieved by having two layers of insulating material surrounding live parts or by using reinforced insulation.

Many wall sockets have earth-pin operated shutters (see image) on the line and neutral lines to prevent children  from inserting conducting materials which may result in electric shock. As double-insulated appliances don't require an earth connection, a  plastic earth pin is molded into the plug in order to open the socket  shutters in place of a normal metallic earth pin.


Typically, the plastic third pin is provided to allow the 2-pin charger to be inserted into the ubiquitous 3-pin sockets...

Nowadays, there is a safety feature in the modern type of switches which has an insulating sliding/blocking shutter in front of the live pin. This shield slides up, only when the ground pin is pressed inwards. 

This helps prevent inadvertent shock to say children, who might poke their little fingers into a live point!

You could cut off the plastic pin, but that'd mean it'd be difficult for you to charge on these type of modular switchpoints.

Warning - The following tip is potentially extremely dangerous, and is being provided only for completeness of information. If you zap yourself dead while doing this, I do not hold any responsibility for that!

One (DANGEROUS!) work around would be to push the ground pin inwards using a thin *wooden* stick while inserting the adapter in. Please don't use any metal or electrically conductive object to do this, otherwise you might risk getting electrocuted and die a horrible death! There is a reason they put the plastic shield around electric points.

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