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Basic Terms: Ground Earth Neutral Etc.

03/19/2014 12:37 AM

What are the conceptual meanings(physics-wise) and practical distinctions(engineering practice-wise) among the following terms especially with regards to Kirchoff's Current Law:

(1) ground

(2) earth

(3) neutral

(4) return path

(5) guard

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#1

Re: Basic terms: ground earth neutral etc.

03/19/2014 1:57 AM

A search engine can define these terms quite nicely.

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#2
In reply to #1

Re: Basic terms: ground earth neutral etc.

03/19/2014 2:26 AM

...or quite ambiguously.

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#3

Re: Basic Terms: Ground Earth Neutral Etc.

03/19/2014 10:10 AM

The difference between no.1 and no.2 is the Atlantic Ocean.

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#5
In reply to #3

Re: Basic Terms: Ground Earth Neutral Etc.

03/19/2014 2:37 PM

I always laugh out loud when I hear that one!

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#11
In reply to #5

Re: Basic Terms: Ground Earth Neutral Etc.

03/20/2014 3:17 AM

Yes. Apologies for the repetition.

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#4

Re: Basic Terms: Ground Earth Neutral Etc.

03/19/2014 11:42 AM

No.3 is the conductor that connects to the star point of the local distribution transformer, providing a no.4 for the difference in currents between the phase conductors.

No.5 is what prevents parts of the body getting into mechanisms that can cause harm to them.

Is there a prize for getting it right?

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#6
In reply to #4

Re: Basic Terms: Ground Earth Neutral Etc.

03/19/2014 2:39 PM

5. could also refer to the drain in a shielded wire...

...why, I don't know...it just is....

I call it a drain

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#15
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Re: Basic Terms: Ground Earth Neutral Etc.

03/21/2014 1:16 PM

you are incorrect. no. 5 is what is done for the queen of England

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#16
In reply to #15

Re: Basic Terms: Ground Earth Neutral Etc.

03/31/2014 10:07 AM

The present incumbent is also the monarch of several other countries as well, including Scotland for the moment. Residents of republics don't often appreciate these things.

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#7

Re: Basic Terms: Ground Earth Neutral Etc.

03/19/2014 2:42 PM

Kirchoff's circuit laws (Kirchoff) didn't reference ground...he dealt with conservation in closed networks/circuits.

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#8

Re: Basic Terms: Ground Earth Neutral Etc.

03/19/2014 6:16 PM
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#9

Re: Basic Terms: Ground Earth Neutral Etc.

03/19/2014 10:29 PM

4) Is the path of the hand through the heart and down the torso and the feet to Earth.

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#10

Re: Basic Terms: Ground Earth Neutral Etc.

03/20/2014 1:16 AM

1). Ground is a equipotential circuit - May be and mayn't be connected to Earth. It is specific to the circuit and embedded on circuit PCB or inside the equipment body.

2). Earth is a firm earth in absolute meaning and it includes various types of earthing for different equipment.earthing is specific again to the ciruit is is designed and installed for.

3). Neutral is the common STAR point of generator which is run all along the phases to get single phse supply to consumer. Neutral potential may varry at places depending on circuit elements and electrical properties of neutral wire. That is why the neutral is earthed just before every circuit / installation where you need lesser variations in supply. If neutral voltage is away from zero it may float during faults in the vicinity causing dame to ciruit components and loads there.

4). Return path - It has reference to which it is used . For earth fault it is current returns through earth which operates the E/F relays. For general working circuits it is return from load. In building lighting they are called "Other half" wires returnimng from appliances to neutral links. Mostly return path is significant for fault conditions, which provides path for current / voltages which in turn operate the trelays for protection. The path is not defined as it deals with Faulty situation and depends on the variety of faults.

5). Guard wire - it is basically a shield . all the inductiion generated voltages are grounded ( or earthed ) to avoid damage to the circuit components or human handling them. Some shields used in coaxials, XLPE cables, drain wires in analog cables are types of guard. In some cases a wire mesh guard is created and earthed - this is generally seen at locations where two transmission l;ines cross causing danger of induction or falling of higher conductor on lower one resulting in severe damage to men and machines.You may call heat sinks as thermal guards.

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#12

Re: Basic Terms: Ground Earth Neutral Etc.

03/20/2014 12:14 PM

A guard is a shield around a circuit. Its purpose is to prevent currents in the ground (earth) from contributing to the measurement; it enhances the accuracy of the measurement. Guards are used in high end DMMs, calibrators, etc.

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#13

Re: Basic Terms: Ground Earth Neutral Etc.

03/20/2014 12:30 PM

A GUARD is normally at the inner conductor potential. So a guard is normally driven. It's used a lot in low current measurements where cables are Triax and have an inner conductor and 2 shields. The inner shield is driven at the same potential as the center conductor. The outer shield is connected to ground/Earth.

This prevents leakage currents within the cable. Graphite within the cable can reduce the triboelectric effect,

A SHIELD is at ground potential and connected at one end to Earth. It's used to reduce RFI. Twisting wires in pairs is used to reduce EMI.

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#14

Re: Basic Terms: Ground Earth Neutral Etc.

03/20/2014 5:02 PM

Ground- the medium that vegetables are grown in.

Earth - Posh English word for dirt.

Neutral - When no one takes responsibility.

Return Path - The way home from the pub.

Guard - The person one meets at home, after being at the pub, who asks, 'Do you know what time it is?'

Mechanical engineers make weapons. Civil engineers make targets!

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