Jan 30, 2008 - Anything & Everything, Science & Technology    5 Comments    14,958 views

2-pin & 3-pin plugs. Why?

ASK! about Anything & Everything

Ever wondered why some of the appliances come with 2-pin plugs while others are 3-pin plugs?

Apparently, when electricity was first introduced into the domestic environment, it was primarily for lighting. However, as it became a viable alternative to other means of heating, plus the development of labour saving appliances, a means of connection to the supply other than via a light socket was required. In the 1920s, the two-pin plug made its appearance.

At that time, some electricity companies operated a split tariff system where the cost of electricity for lighting was lower than that for other purposed, and this led to low wattage appliances (e.g. hair dryers, vacuum cleaners etc.) being connected to the light fitting.

As the need for safer installations grew, three-pin outlets were developed. The third pin on the outlet was an earth pin, which was effectively connected to earth (this being at the same potential as the neutral supply line). The idea behind it was that in the event of a short circuit to earth, a fuse would blow, thus disconnecting the supply.

 The reason why we are now stuck with no less than 13 different styles of plugs and wall outlets, is because many countries preferred to develop a plug of their own, instead of adopting the U.S. standard. Moreover, the plugs and sockets are only very rarely compatible, which makes it often necessary to replace the plug when you buy appliances abroad.

 Source: http://users.pandora.be/worldstandards/
electricity.htm

 For more information on the different types of plugs used in different countries, you can visit this website: http://www.travel-images.com/
electric-plugs.html

Originally answered by Ms Eleaner Ang, Librarian, Adult and Young People’s Services

Yen_ASK_Pic.JPGPosted by Yen Yen Toh, Librarian, Adult and Young People’s Services

Found this question interesting? What do you think? Post your comments.
If you have a different question, please email to ask@nlb.gov.sg instead of sending a comment.

5 Comments

  • [...] davidrothman.net wrote an interesting post today onHere’s a quick excerpt [...]

  • good work. would have been better with pictures of the different types of plugs.

  • You didnt answer the ques.

  • Some appliances still use 2 pin plugs. Why is it still safe to do so?

    • Hi, according to a document on the SPRING Singapore web site (www.spring.gov.sg), certain 2 round-pin Mains Plugs are suitable for use in Singapore. The 2.5AMP 2 round-pin Mains Plug commonly used for electronics appliances such as TVs, DVDs, and audio sets do not rely on earth as a form of protection, and therefore only 2 pins are needed.

      You may refer to the article for more information here: http://www.spring.gov.sg/QualityStandards/CPS/SAT/Documents/Mains_plugs.pdf (last accessed September 9, 2012)

      You may also email us at ask@nlb.gov.sg if you have further queries :)

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