Dear friends,
Could you please explain me in a quick way, what is the function of the ground wire ?
I measured the voltage between the neutral and ground wires, and I got a value of 4 volts. Is this a acceptable value?
What is the ideal value ?
Many Thanks
Its quite possible you could have a small voltage drop on a neutral wire that is under load. Quite normal in fact.
I'm assuming you are talking about the wire connected to the third prong on the plug or the wire in the house wiring that connects to the round hole in the receptacle. It is there for safety, to prevent you from getting a shock due to some defect in equipment you are using.
As Bob said, you can have a small voltage drop on the neutral, which would cause a small voltage difference between neutral and ground. But you also need to make sure you are measuring with the proper procedure. Many people just connect a DMM to ground and neutral - and that is the wrong way to do it. Connect a ~100 watt test lamp from ground to neutral, and measure the voltage across the bulb. If the measurement was properly done, then
4 volts is a little higher than it should be on a 120 VAC circuit.
There is no "official" ideal value, although you could say ideally it should be close to 0 volts. However, as both a practical and theoretical matter, any conductor with a current flowing in it will have a voltage drop across it, so it is not at all unusual to find a small voltage between the neutral and ground when measuring correcty.
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