Grounding - Understanding what it really is and does.

Hi

I'm a bit confused in understanding what ground really is.
If I have a DC circuit where the negative terminal is used as ground and the current flow is negative to positive (I'm using conventional current flow for sake of argument).

If a component has a current passing through it and is "grounded" would the negative terminal have a different amount of electrons?

Another example is if I'm charged and I touch a piece of metal then I ground through that metal right? Does this now mean that the metal has an extra amount of electrons which means it's no longer neutral?

Could someone explain the difference between ground and earthing.

Thanks

That's a pretty big subject. First of all, in electronics we usually talk of current flowing from positive to negative (I know, I know, electrons flow the other way.) You can talk about electron current, but you'll just confuse everybody on this board. (You'll confuse me, at least.) So let's say current flows from positive to negative.

I think you are confusing 'charge' with 'current' (which is charge/time) . In a DC circuit you wouldn't (generally) say that one point has more electrons than another, the DC current around a loop is the same at every point in the loop.

Now you need to understand the difference between common and ground. In your proposed circuit the negative terminal is "common", and unless you have it attached to a copper rod banged into the earth (the planet) it's not really 'ground'. To confuse things more, here in the US we call it ground; in the UK (and elsewhere) it's called earth. And then we have something called 'earth ground'. Confused yet?

Just look at it this way: there's a common point in your circuit that all other voltages are referenced to; you can call this 'ground' if you like, but 'common' is a more accurate term. Someone once said to me: "Ground is where you plant tomatoes."

To answer your other question, when you discharge yourself into a piece of metal, you ARE transferring electrons from one place to another. These electrons will eventually bleed away to the earth. But that metal that you discharged into may change it's voltage level with respect to earth (and other points in the circuit). This opens up the whole world of ESD (ElectroStatic Discharge).

So if a component such as a resistor, delivers a lower voltage to another component (say a transistor) and this is the final operation of the circuit it then must go to "Common" to create a PD to finalise the circuit?

So the negative terminal is never charged, it is just there to create a PD?

So if I'm right, when a battery loses its voltage its because the PD has dropped due to the work done, but both -ve and +ve will have a lower PD at a lower ratio of the original PD?

Thanks for your help Barry.

What's a "PD"?

barry said:

What's a "PD"?

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Potential Difference (PD) I think he refers to

So the negative terminal is never charged, it is just there to create a PD?

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Negative terminal is just used as a reference. For a current to flow you have to create a loop, otherwise a "point" is floating with no reference to anything.

DrWhoF said:

Negative terminal is just used as a reference. For a current to flow you have to create a loop, otherwise a "point" is floating with no reference to anything.

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Yes I understand the reference point now. This makes measurement precise with regards to voltages at certain points.

My trouble is with current flow. Take the simple circuit of a battery and the the lamp.
The battery is 9volts and the lamp is attached to the circuit in series, so it receives the full 9volts. The thing is electrons are moving from one terminal to another and that confuses me because the negative terminal is regarded as ground in a circuit. The thing is reference ground should always be 0 volts right, but it seems that electrons are being lost and gained which means the terminals still have a charge right?
So is the negative terminal just a pathway to create the loop when we design circuits?

Thanks

You are confusing charge and voltage. Voltage is relative. It's the difference in charge between two points.

barry said:

You are confusing charge and voltage. Voltage is relative. It's the difference in charge between two points.

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Ah! I think I have it now. So the difference in charge creates the voltage state. If either or both ends of a battery have no differential charge then there can be no voltage because there is no potential difference?
The charge will cause current to occur if a loop is created between the opposite terminals.

I thought that that electrons moved to positrons as they do with the glass rod and silk experiment as in a short circuit, but its the actual movement of electrons in the copper wire that move to create work in the light bulb which is a resistor and stops the circuit from shorting.


Thanks

my man remember this analogy water in a tank is different from water flowing in the pipe with a partly closed tap

charge is water in the tank

current is flowing water in the pipe

tap is the voltage that drives the current in the direction of flow

now the no of electrons in a metal bar is charge

the amount of flowing electrons in time is current

the force that drives the current in a direction is called voltage

jeffrey samuel said:

my man remember this analogy water in a tank is different from water flowing in the pipe with a partly closed tap

charge is water in the tank

current is flowing water in the pipe

tap is the voltage that drives the current in the direction of flow

now the no of electrons in a metal bar is charge

the amount of flowing electrons in time is current

the force that drives the current in a direction is called voltage

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Yes I think that clears it up but I can see why it's so confusing:

charge is water in the tank = this can be either positive negative or neutral and is relative to the atomic state of an element or compound

current is flowing water in the pipe = This is relative to the electron and the negative moving to positive

tap is the voltage that drives the current in the direction of flow This is a relative term and is the difference of charge between two points

now the no of electrons in a metal bar is charge I thought a positron can also be a charge, such as in silicon and NPN, PNP transistors?

the amount of flowing electrons in time is current= Amps, which is the amount of electrons moving past a point in one second

the force that drives the current in a direction is called voltageand that's the difference of charge between two points.

I think I have it now, please tell me if I'm still wrong.

Theses terms aren't as simple as I thought.

P.S. When an electron moves to a positron as negative moves to positive in a battery does that mean the charge decreases?

Thanks Jeffrey

Music Manic said:

positron

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I think you mean proton.

godfreyl said:

I think you mean proton.

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:lol: Yes I was trying to make myself look clever....

Music Manic said:

Yes I think that clears it up but I can see why it's so confusing:

charge is water in the tank = this can be either positive negative or neutral and is relative to the atomic state of an element or compound
charge in general of electron is negative
proton is positive
and neutron is neutral
current is flowing water in the pipe = This is relative to the electron and the negative moving to positive
primarily flow of current is taken in a direction opposite to the direction of motion of electrons
that is a bit confusing but it is true
tap is the voltage that drives the current in the direction of flow This is a relative term and is the difference of charge between two points
voltage is not exactly that
now the no of electrons in a metal bar is charge I thought a positron can also be a charge, such as in silicon and NPN, PNP transistors?
positron is not considered in trannies only holes are considered and in general when it comes to current in pure metallic conductors charge always represent no of electrons.

in semi conductors holes and electrons are considered that is it

the amount of flowing electrons in time is current= Amps, which is the amount of electrons moving past a point in one second
true
the force that drives the current in a direction is called voltageand that's the difference of charge between two points.

I think I have it now, please tell me if I'm still wrong.

Theses terms aren't as simple as I thought.

P.S. When an electron moves to a positron as negative moves to positive in a battery does that mean the charge decreases?
the charge you know never decreases and all
Thanks Jeffrey

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you forgetting that it is impossible for an electron with out having very high potential to reach the nucleus of the atom where protons are present

this is because current is generally due to motion of valence electrons found in the outter shell

the energy of the electrons here is very low and this is not sufficient to go towards a nucleus (screening effect of electrons in inner shell)

my replies are in colour do check it out

Great stuff Jeffrey. I'm beginning to understand the energy of atoms now.

You're a gent!

"Ground" in electronic terms is just a common potential. It can be floating or connected to another common potential.
These common potentials are useful because you need a reference point for supplying power and shielding from interference that may be conducted or radiated from different potential reference points.

"Ground" in electrical terms is a common potential that is connected to an "Earthed grounding rod" for local safety reasons.
It becomes a conduit for lightning discharge and a reference point for the transformer neutral , which is also connected through a grounding rod for safety reasons.

The ground is not used for AC power transfer but it is used for noise filtering. As much as 0.5mA of AC noise per 3-pronged powered unit with line filter caps may be conducted from line or neutral to ground wire via filter caps to suppress conducted noise in either direction.

SunnySkyguy said:

"Ground" in electronic terms is just a common potential.

It can be floating or connected to another common potential. These common potentials are useful because you need a reference point for supplying power and shielding from interference that may be conducted or radiated from different potential reference points.

"Ground" in electrical terms is a common potential that is connected to and "Earthed grounding rod" for local safety reasons.

It becomes a conduit for lightning discharge and a reference point for the transformer neutral , which is also connect through a grounding rod for safety reasons. The ground is not used for AC power transfer but it is used for noise filtering. As much as 0.5mA of AC noise may be conducted from line or neutral to ground wire via filter caps to suppress conducted noise in either direction.

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Yes Sunny grounding seems to be a slack term. When something "Earths" it discharges a potential that could be hazardous. My problem was when I saw the negative terminal of a battery (in a schematic) as the ground. I didn't realise that the true ground would be, for instance, the ground of a 1/4" audio jack, or the ground of a PCB board. But then again, the larger the voltage the larger the size of a ground right? If lightning struck a small metal sheet it would still fry it but if it struck the eiffel tower there would be more space for the charge to disperse. People think the Eiffel tower would be at zero volts but that is not true because the charge of lightning has shed it's charge elsewhere? The law of physics states nothing is ever lost it is just transferred.

I was confused because if a battery was the ground point, which it isn't right!, it would cause a problem because it would be losing electrons, which are being drawn by the positive terminal of the battery, and thus, lose it's charge gradually and also the P.D will lessen. It will still create current for the circuit but voltage will drop until it "dies"

Thanks

Music Manic said:

Great stuff Jeffrey. I'm beginning to understand the energy of atoms now.

You're a gent!

Click to expand...

it is really nothing its my pleasure to help

- - - Updated - - -

Music Manic said:

Yes Sunny grounding seems to be a slack term. When something "Earths" it discharges a potential that could be hazardous. My problem was when I saw the negative terminal of a battery (in a schematic) as the ground. I didn't realise that the true ground would be, for instance, the ground of a 1/4" audio jack, or the ground of a PCB board. But then again, the larger the voltage the larger the size of a ground right? If lightning struck a small metal sheet it would still fry it but if it struck the eiffel tower there would be more space for the charge to disperse. People think the Eiffel tower would be at zero volts but that is not true because the charge of lightning has shed it's charge elsewhere? The law of physics states nothing is ever lost it is just transferred.

I was confused because if a battery was the ground point, which it isn't right!, it would cause a problem because it would be losing electrons, which are being drawn by the positive terminal of the battery, and thus, lose it's charge gradually and also the P.D will lessen. It will still create current for the circuit but voltage will drop until it "dies"

Thanks

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you are partly right in telling the size of the gnd required it is not that eiffel tower is big and a lightning arrestor in the local market are also big it is the amount of ions which are induced around them by the cloud

when a cloud having potential passes it (indution principle) induces charges in metals

a sheet of metal provides lesser charge when compared to needle like or pointed objects and thus lightning tends to move towards those pointed objects this is what is used in a lightning arrestor

all other points are real the electrons from the cloud gets transferred to the earth below us that is correct

There should be no positrons or protons involved in this discussion. What you really mean is "holes".

barry said:

There should be no positrons or protons involved in this discussion. What you really mean is "holes".

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Well the proton charge does create a PD to attract electrons which creates current. Holes are to do with doping silicon and they create a positively charged state but in a way which is deficient of an electron. It doesn't mean a proton has been added.
It's the state of whether there are an excess or deficiency of electrons which states what the charge is.