circuit breaker of a 3 pin plug? ( for my coursework so plz answer)

[luvmexx]

how do circuit breakers work for a 3 pin plug? and how have they become safer than in the past? also any other info on 3 pin plugs would be great thanx its for my gcse coursework thanx xxxx

[Tweed]

There is a fuse in a 3-pin, 13 amp plug, which is probably what you mean. It is a thin piece of wire enclosed in a cartridge, that will melt if a current greater than its stated value flows across it.

[New Forester]

You might also be thinking of a plug-in circuit breaker. This is a safety gadget which plugs in between the socket and the plug of the(usually outdoor) appliance. It cuts the supply if, say, you cut the flex with the mower. It's called an RCD -- Residual Current D... (something, can't remember what). There are similar things in modern consumer units ("fuse boxes"). The RCD constantly checks whether the current returning down the neutral wire exactly matches that going up the live wire. If any at all (milliamps) goes to earth instead (such as through you when you get a shock), it immediately (milliseconds) cuts the supply -- quick enough to stop too much harm. A fuse such as that in an ordinary plug only blows if there is a continuous high current -- 13 whole juicy amps, or fewer with a smaller fuse. It takes quite a good chunk of a second to do it, and by that time you might be dead. An RCD would not help you if the current was going straight from the live to the neutral through you, as the two currents would still match perfectly. So don't try that at home -- it has to be to earth. Remember that the "13 amp" rating of a plug is a maximum. The actual fuse you use should depend upon the appliance -- 3 amp for lighting, 5 amp for medium duty (small telly?), and only 13 amp for heavy duty stuff like a washing machine, heater or iron. Too big a fuse might mean it started a fire before it blew. Oh yes: D for Device.

[ajmmac]

try this site http://electronics.howstuffworks.com/circuit-breaker.htm