the main purpose of the grounding pin in a three-prong plug for an appliance is to_______.?

Question

a.boost the current flow to the appliance
b.prevent short circiuts
c.prevent electrical shocks
d.allow for variable speed operation

Answer 1

c

There was a time before plastics when the cabinets of most electrical appliances were metal. if one side of the power cord were to contact the cabinet it would not cause a short but it could give you a shock. The third wire safety ground is connected to the cabinet so that if either side of the power cord contacts the cabinet it WILL cause a short and trip the breaker eliminating the shock hazard by disconnecting power!

I am NOT suggesting YOU do this, but perhaps someone you know can do it safely... Plug a Three prong cord into a wall outlet, touch the black or white wire with the bare safety ground, the breaker should trip.

Answer 2

there's both history, and purpose. in the past, you could get a shock when you touched either wire, and the ground. today, that's no longer the case. with polarized plugs, there is only one 'hot' wire. the other is, for all intents and purposes, ground. BUT, if you have a 220 line, for your oven, for example, both sides are hot. what happens is that the power lines into your house contain +110, neutral, and -110. and 220 is between the +110 and -110. many years ago, i stayed in a hotel that had fuses on all 3 lines, which is very wrong. and the middle fuse blew (from old age, presumably). so the current into the hotel on the + side went to a series or rooms, and back to the neutral line, which was no longer connected, then to the remainder of the rooms, and out the other line. the reason that's done is to balance the current, which is a good thing, because it reduces the max current in any specific line, and also, i believe, reduces the utility bill. at any rate, the resolution to the problem was to put a piece of copper pipe across the neutral line. so, today, you really don't need the 3rd line, with new appliances. but there are some places that don't have polarized plugs, in which case, the ground wire is still needed (or at least good to have). and there are some people that just like having the ground wire.

Answer 3

In an appliance, the ground wire is clamped to the housing or metal cabinet of the appliance (think washing machine).

a. is not right because the ground wire does not supply current to the appliance. It is a safety feature only.

b. is not right because a short is an unintentional connection between the main current carrying wires (hot and neutral), which does not involve the ground wire. A short will usually result in a tripped circuit breaker, or a fire. You could also have a "short to ground" in which the hot wire has cross-connected to the ground wire, usually because a portion of bare hot wire touches the cabinet. However, in that instance, the ground wire does not "prevent" a short - the short still happens, it is just controlled and bled off by the ground wire. Thus answer (b) is tricky because the ground wire prevents HARM from some short circuits, but it does not prevent the short from occurring. :)

c. is the most correct answer of the choices you offered. If the live wire should somehow touch the metal casing of the appliance (due to cut insulation, etc.), the ground wire provides a means to bleed the current away from the appliance back to ground, in effect providing an alternate "neutral" wire. Without the ground wire, the appliance might charge up to 120V and shock anyone who touched it - in effect, you would become the ground wire to take the current to ground through your body. However, grounding a loose connection provides one path for the stray current to bleed off. You could still get shocked (although much milder) because current is still flowing through the appliance cabinet, and a fire could still start because an uncontrolled current could flow from the hot wire to the ground.

d. is not correct. Again, the ground wire normally is dormant and carries no current. Variable speed operation is accomplished through multiple taps in the motor windings, or through a sophisticated electrical controller.

===

There is a second device, called a "ground fault circuit interrupter" breaker that acts as another type of safety. Many people mistakenly believe that a GFCI watches for current on the ground wire and trips the breaker if it sees any. In fact, the device does not even use the ground wire (the wire passes straight through the device), but watches for a differential in current "coming in" through the Hot lead, compared to the current "leaving" through the Neutral. If you should manage to touch the hot wire, you would get shocked without a GFCI, because you bypassed the ground wire and touched the hot wire directly. A GFCI will detect the current leaving through the Hot lead and grounding through your body, and see that a matching current is not returning along the neutral wire, and thus trip the GFCI breaker.

If the GFCI watched for current on the ground wire, it would not detect you getting shocked when you grabbed the hot wire alone, and you could get fried even with a GFCI in place. That's why they look for "lost" current, not current down the ground wire.

The electrical and building codes generally require that both a standard breaker and a GFCI breaker be installed at any outlet where water might be present (on the floor). So bathroom, kitchen, and outdoor outlets of newer homes are all protected by both types in these locations.

Answer 4

The stated purpose of the grounding circuit is C.

HOWEVER, the reality is that the grounding wire vastly increases your chances of being shocked. With the grounding wire typically connnected to metal appliance housings and electrical junction boxes, the chances are much greater that your body will be grounded by touching something in the area. Being grounded is one of the 2 requirements for getting shocked. The other is touching some OTHER part of your body to a 'hot' wire.

The code requirements for grounding wires are written by the very people who will benefit by selling you 50% more copper in an extension cord, etc. The grounding wire is politics masquerading as BAD SCIENCE.

How come the USA is the only place in the world where this is required? All over Europe they have only 2 wires, and they're running 220V.

Water: Has always been given a bad wrap based on false information. Fresh water is one of the best INSULATORS around. However, since it was traditionally carried to the point of use in metal pipes (good electrical conductors), people were getting shocked by having one hand on a metal sink faucet and the other in the toaster. Then they blame it on the water. Those metal pipes run through the GROUND and are therefore nearly perfectly grounded. There is a lot of momentum up against water and the teaching of it as a dangerous thing around electricity. Even James Bond affirms this when he dispatches 'OddJob' by throwing a space heater into the bathtub with him. HOGWASH.

Take THAT, all you victims of the M-I complex........

Answer 5

The grounding plug leads to a wire that runs through your house and eventually down to a metal rod that is literrally just stuck in the ground. This allows excess charge that builds up in the alliance to be dissapaited safely into the ground, which is generally receptive (but not terribly conducive) to electrical charge, and usually has a slight positive charge itself.

This prevents the cricuits of the device from being overloaded, resulting in electrical shocks and short-circuits. I would say C, since by and large, the grounding wire prevents static electrical shocks far more often that it would prefent large shocks and short circuits.

Answer 6

the answer is C

from wikipedia...In 1928, the three prong plug was invented by Philip F. Labre, while he was going to school at MSOE (Milwaukee School of Engineering). The story goes that his landlady had a cat, the cat would knock over her fan when it came in the window and when she would plug the fan back in, she would get shocked. Philip figured out that if the plug was grounded, the electricity would be controlled. He applied for and was issued a patent for grounding receptacle and plug on June 5, 1928. U.S. Patent 1,672,067

Answer 7

To prevent elecrical shocks. (C) IF an appliance gets a SHORT in it, the voltage can make 'live' the body of the appliance, and if you touch it and happen to be grounded, you will get a nasty shock, sometimes fatal.
The ground wire and ground prong is GROUNDED onto the body of the appliance and carries any stray voltage directly to the ground (also connected to the neutral) without going through your body.

Answer 8

C.

The ground pin connects the metal parts of the device to ground. So, if something happens that would normally cause the metal in the object to carry current when it's not supposed to, that current will flow to ground instead of your hand.

Answer 9

Hope you do well on your school assignment. I kinda hope your teacher is into yahoo Answers as well.

Answer 10

None of the above, its so you can't use the cord for Xmas tree lights!