Plug

[Justin]

How come Britain uses the 3-pin electric plug and most of the rest of the world just use 2?

[Ed Ancona]

I haven't taken a survey, but I would expect that most countries have provision for 3-pin electric plugs. The third pin is to assure a safe grounded (earthed, if you're British) connection to the frame of the device. In the US, the standard wall receptacle has two parallel slots for the plug blades, and a third round hole for the round third pin on the plug. Manufacturers will equip their devices with a three-wire cord and a three connection plug if the device requires such. Most electric lamps or small devices would not need the third ground (earth) connection. In France the plugs have two male blades and a female round receptacle. The wall receptacle has two female (I hope this site is OK for the young) blade receptacles and a round pin. Usually the ground pin is longer to assure that the ground connection is safely made first just before the power connections are made. Anyone want to survey all the other countries? I'd bet that most of them have some variation of the three-pin plug and receptacl

[Ed Ancona]

Correction to my description of the French plug: The French plug has two round pins (not two blades) and a round hole which mate with the opposite on the wall receptacle. The longer round pin on the wall receptacle makes the ground (earth) connection before the two shorter power pins connect.

[anexperience]

There are some countries who don't use an "earth" (connection to ground). There are arguments about whether it is a good thing or not, without the "earth" you can grab hold of a "live" wire and nothing happens! (no shock) where as with an "earth", well you probably have had an electric shock, so you will know. Also electrical goods that are "double insulated" need no earth, as the casing cannot become live and so you cannot get a shock.

[Paul Frank]

actually "double insulated" means the appliance is insulated to twice (i.e. double) the required standard

[midavies]

Blame it on history and the Institute of Electrical Engineers who regulate the Electrical Installation industry. There are other issues here: a 13A plugtop is fused, which is unique and allows use of a ring main system rather than direct wiring,

[Luma]

answers are off on a tangent here, but the reson for earthing is to eliminate the possibility of line voltage occurring, and to render all extraneous metalwork to near 0 potential. Line voltage being 415V between 2 phases in a 3 phase system The other is Phase voltage, 230v of a single phase system.

[bigbagz]

No one as yet has mentioned the different sizes of voltage. Not many countries have all sockets at 230 volts. The canadians do have some, but they also have mainly 115V sockets, I think, for the less "heavy duty" appliances. Certainly most places in europe seem to have 115V. This smaller voltage should, I think, pose less of a threat to life due to the relationship of resistance=voltage/current. Any human has a given resistance (as indeed does and object at a fixed temperature) and therefore the higher the voltage applied, the more current will be pumped through the person. Voltage may well have a large effect on the body just due to higher voltages doing more to mask the smaller voltages used in the nervous system. The higher risk of damage from electric shocks would be good cause for an earthing system. The theory in the earth being that there is negligeable resistance in the earth compared with a human so the electricity "takes the easy option" and flows to the ground through the earth, not the person. I don't think this fully answers the question, but hopefully may help point in the right direction.

[GeorgeR]

The Institute of Electrical Engineers must take the blame for Britain being out of step with the rest of the world in the design of its electrical fittings. The square pin plug is a huge and ungainly device. European plugs elswhere are neater AND with 3 connectors where required. The earth is normally a contact on the side of the plug. You unfortunate British travellers have to travel with all your adapters to use electricity anywhere else. Time the EU did something on these lines, instead of straightening cucumbers! George Rush, Portugal.

[Bahbill]

Further to 'anexperience's answer. If the circuit capacitance is sufficient you can still get 'zapped' on an unearthed system. It only takes 30mA to kill . Unearthed systems do have their advantages but personnel safety is not foremost in Industrial applications.

[...77]

Cos the rest of the world is stupid