Why do we need an earth wire at our homes?

[Flyingsparrow101]

Hi guys,
I was just wondering why do we need an earth wire for our homes why do things like extension cables need an earth wire?

 

[damasvara]

^+1. To be more detailed, since the electricity (AC voltage) needs to be earthed, any medium in contact will be the conductor. Including the human body. For low wattage, the shock is minimum. The higher the wattage, the stronger the shock will be.

 

[alyoshka]

Actually, an earth wire is like a antistatic wrist band that we use when we fool around with computer equipment.
It works as a siphon for extra electrical charge around any electrical appliance.
In case there is a leak somewhere in the equipment, the current tends to stay in it and if a human being was to come in contact with the equipment he is going to be the easiest route for the electrical energy to pass thru , thereby, like Dipanker said, to avoid a situation like that , all houses have a earth wire to drain excess current or minor leaks of current in any equipment so as to save us from getting shocks every now and then...

 

[Flyingsparrow101]

Thank you all for your replies, but what it means is that if you come into contact with electrical charge you won't get shocked, right?

 

[alyoshka]

No!!!!!!!!! You will get zonked if you come in contact with electrical charge irrelevant of earth wiring.
Earth wiring is not meant for you, unless you're plugged into one of the sockets... which I doubt......
It is for the appliances not for humans....... for humans we have rubber insulated boots and rubber non conductive gloves to avoid the kick......

 

[damasvara]

^ Well, as someone who experienced it first hand, I'd say, you will get shocked.

Basically, the human body is a natural electrical conductor, with our feet touching the ground, the shock effect becomes even greater, as we become the ground connector. I'm saying this because, like I said above, I've experienced it first hand. Boy, it sure stings! :lol:

As for alyoshka analogy, I think he misunderstood it with ESD (electrostatic discharge). ESD is to eliminate the human's body from creating electrostatic charge, which will only affect sensitive electronics components like CPU or motherboard. Plus, we don't touch the components at their active electrified state. Not if we still value our lives. 😀

So, if you want to avoid being shocked, ground the designated item. The most common are refrigerators and, of course, PCs. For example, I use a copper wire connecting the back of my PC case to a nailed wall as the grounding method.

You're welcome to try if you like, the "shocking experience" that is. :lol:

 

[moody89]

Earthing serves serveral purposes. Firstly, any exposed or extraneous conductive parts are connected to 'earth' so that, in the event of a fault, a live cable which touches an earthed metallic object will raise that metallic object to the same potential as the live part. Here in the UK we work with 230V, so a live conductor would be at 230V potential. If a conductor were to touch an earthed metallic object then that object would also be at 230V potential. If there's no potential difference, no current flows hence there is no shock.

This very rarely happens in reality though, since MCBs, fuses, RCDs and the like will operate almost instantaneously when a live conductor touches an earthed metallic object. And this brings us on to the next reason for earthing which is actually to cause a lot of current to flow under fault conditions. Sounds backwards, but it makes sense when you think about it. In the event of a fault you want the MCB, fuse etc. to operate as quickly as possible to isolate the supply. By providing an earth return path for the current to flow back to the supply transformer, the MCB/fuse will operate much quicker and knock off the supply before any damage occurs.

Nowadays, the more sensitive RCDs are used which detect inbalances between Live and Neutral and will also isolate the supply if this inbalance reaches a certain level.

As mentioned, earthing can also be used to discharge static electricity when we work on computers etc. However in the more industrial scenarios, a non-conducting location is more likely to be used where precautions are taken so that nothing conducts electricity, again not allowing a potential difference to occur.

It's also interesting to note that computer systems use the earth wire for their general usage. I'm not exactly sure of the in's and out's of it, but if you have a whole bank of computers protected by an RCD, the RCD can often trip for no reason other than because of the current that is leaking to earth.

 

[Flyingsparrow101]

Thanks!!!

 

[Flyingsparrow101]

Best answer selected by Flyingsparrow101.