Why do plugs have ground

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Most other plugs I encountered have three prongs - hot, neutral and ground I assume. For example all BS plugs have one. What reasons are there for those differences is it due to V vs. Many appliances in the USA and elsewhere have two-prong plugs because they are "double insulated. Double insulation provides very effective ground fault protection that is less expensive for most products. The fact that the US voltage for domestic wall-plug use is volts offers a small amount of additional safety vs.

Double insulated or class 2 electrical appliances are products that have been designed in a way so as not to require a safety connection to electrical earth These products must NOT have a safety connection to Earth.

These products are required to prevent any failure from resulting in dangerous voltage levels becoming exposed causing a shock etc. This must be done without the aid of an earthed metal casing.

Ways of achieving this include double layers of insulating material or reinforced insulation protecting any live parts of the fitting. There are also strict requirements relating to the maximum insulation resistance and leakage to any functional earth or signal connections of such appliances. Products of this type are required to be labelled "Class 2," "Class II,", "double insulated" or bear the double insulation square in a square symbol.

In order to apply the UL or ETL label, the manufacturer must have product design evaluated and samples tested in the independent laboratory or have their own testing and review results evaluated by the independent laboratory.

In either case, they must maintain a contract with the independent testing laboratory that includes periodic, un-announced inspection of their manufacturing facility and its quality assurance procedures. BS plugs always have a pin in the earth position to operate the shutter mecahnism and to enforce polarity.

However on some non-rewirable plugs and wall warts this pin is made of plastic reffered to in the BS standard as an "insulated shutter opening device". Even when the pin is present and made of metal it may not actually be connected to anything. In my experiance desktop PCs always have an earth connection. I will admit I haven't spend a whole lot of time in america but image searches for desktop PC power cord show a bunch of grounded amerian plugs and no ungrounded ones.

Laptops tend to be more variable, years ago they all used the two-prong figure 8 inlet but an increasing number seem to have moved towards the 3-pin cloverleaf inlet. Small power supplies for phones and tablets generaly don't have an earth connection. Again from what I have seen this is true on both sides of the pond. I do get the impression that the US used class 0 appliances which are not "single fault safe for longer than other countries did but modern stuff will almost certainly be class 1 single fault safety provided by earthing or 2 single fault safety provided by "double or reinforced insulation".

Mostly cost Three prongs are harder to make so cost more. There is no dictated standard in North America that a plug on the end of the cord MUST have three pins regardless of insulation type.

Further, there are countless legacy outlets that have no hole to plug the ground pin into, even in relatively modern buildings. So adding the third pin can actually increase your product return numbers and reduce your market share. The North American outlet system is rather old. Plugs never seem to fit right and it is really easy to touch the live pins while inserting and removing the plug from the outlet.

Your email address will not be published. Save my name, email, and website in this browser for the next time I comment. Mick asks: Why do some things have plugs with two prongs and others need three to work? What is the difference between two- and three- pronged plugs? Why do television plugs have only two pins? Enjoy this article? Answers Articles Featured Facts Science.

Ciampino March 2, pm. So what is the proper term for accidently getting killed by electricty? Dallas Halcomb January 28, am. Rob August 16, pm. Mobile Newsletter banner close. Mobile Newsletter chat close. Mobile Newsletter chat dots. Mobile Newsletter chat avatar. Mobile Newsletter chat subscribe. Everyday Tech. Updated: Feb 11, Three-prong plugs help guard against electric shock. Existing two-prong receptacle outlets are legally allowed to remain according to the National Electrical Code and can be replaced with another two-prong receptacle where a ground connection what a third prong plugs into does not exist.

Why do we use three prong plugs? A three prong plug is designed so that electricity can be safely supplied to electrical appliances. The third prong grounds the electricity to protect anyone who uses the metal-encased appliance from electric shock. Can you cut the third prong off? Technically nothing happens if you cut the third prong off. However, you've disabled an important safety feature that protects you from electric shock if a wire comes loose.

Are plug adapters safe? No, not particularly. While many people use ground plug adapters, it's not really safe for you, your home, or whatever you're plugging in.