# Can earth Short circuit?

1. Mar 5, 2012

### Godwin Kessy

Can a short circuit occur when a neutral wire is earthed, example a man touches a bare neural wire with bare hands..? And is the effect different for alternating and direct current?

2. Mar 5, 2012

### Averagesupernova

In the U.S. the neutral is already connected to the earth with a ground rod at the transformer and at the service entrance of the building. So what do you think? DC doesn't really apply here does it?

3. Mar 6, 2012

### Godwin Kessy

I never thought i could not have any idea on this... What i know when the circuit is completed.. meaning the live connected to neutral.. Current flows whether it's dc or ac.. and earthing a device as i knew is only due to grounding the static charges that might result in the metallic parts of the device.. A challenge came up when a friend of mine just said that the body of the car works as neutral... Okay it's possible since it's a conductor but.... is it not going to be harmful? There is where the question arose...

4. Mar 6, 2012

### psparky

The frame of a car does act as ground. The negative terminal of the battery is connected to the frame of the car. It's been done this way for a hundred years. It's very convenient as ground is always available no matter where you are in the car.

It's not harmful, because if you do happen to touch hot and ground at the same time you feel 12 volts.....you feel essentially nothing unless you are soaking wet maybe.

All potential hots come from a fuse block as well. So in the case of a dead short....you simply get a blown fuse rather than a bunch of wiring on fire.

Last edited: Mar 6, 2012
5. Mar 6, 2012

### jim hardy

Earth can be though of as just another wire that goes everywhere.

If it becomes part of your circuit, current can flow through it.

Sparky's automobile is separated from earth by the rubber tires which are very good insulators. So the only current likely to flow between a car battery and earth is that "static" charge you feel on cold dry winter days when exiting the vehicle.

"Ground" is an unfortunate term for circuit common because it infers earth.
Usually circuit common is not "earth" , though it can be tied to earth as it is in residential wiring..

old jim

6. Mar 6, 2012

### psparky

This is also why your automobile is one of the safest places to be during a lighting storm!

7. Mar 6, 2012

### Averagesupernova

The very short distance from the chassis to the ground is miniscule comparted the distance the lightning jumps from the sky so the rubber really doesn't do all that much. The reason the automobile is safe is because it forms a faraday cage.

8. Mar 6, 2012

### psparky

9. Mar 15, 2012

### Godwin Kessy

Hallow guys so far am not satisfied at all.... I now realize i require a big concept that i ever had from you guys.... What I know earthing commonly means the return path for electric current, which is normally common... or can be grounding(connecting to the earth-planet)... Please guys get me here... the problem comes... can there be a flow of electric current between a a source(live wire) and grounding (earth-planet as have spoken at earlier).... And how is that possible while am sure the ground (earth) cant form a complete circuit with the source voltage(live wire)... By this challenge am saying that.... Earthing or having the home appliances grounded doesn't help when short circuiting occurs to the appliance... other wise the earth wire has been connected to the neutral to some place... Is any one getting me clearly??
And for that reason.. earthing is only valid for static charges and not the flow of current??
Any objection??

10. Mar 15, 2012

### sophiecentaur

The car body is metal - just like wire. Most / many auto electrical devices are fed with a single (+) wire and the return is via the car body (earth). The (black, often) lead from the battery is usually bolted to the chassis very close to the battery and takes all the return current.

Some devices have two wire feeds (+ and Earth). Many car body parts, these days, are plastic in which case, this is essential for equipment mounted on them.
The word 'neutral' is not used in DC circuits because it has a specific meaning for AC supplies.
Also, in your first post, you talk of a man 'shorting' to earth. People have much too high resistance to be able to provide a short circuit. Some current may flow - that's all.

11. Mar 15, 2012