# Meaning of the term 'grounded' and direction of electron flow

Hello all,

I would appreciate any help clearing up some confusions I have with the term 'grounded'. I am aware that when an electron is grounded it loses its charge and reverts to a low energy state. On a battery we have a positive and a negative (GND) terminal.

My confusion is with the concept electrons move from the negative terminal (where there is a surplus) to the positive, doesn't this conflict with the definition of 'grounded' as how can electrons move when they are at a low energy state?

Many thanks,

Electricity flow is generally treated as going from Positive to Negative for uniformity of discussion. In actual reality the electrons move from negative to positive.

Technically electrons never lose their charge, if they did they would cease to be electrons. They can sometimes combine with positive ions to produce a molecule with a net zero charge.

Back in the day, people thought electricity was the movement of positive charge. It was later discovered that it is actually (or most commonly) the movement of negative charge in the opposite direction. The weird thing is that the laws of physics governing electricity are completely (or nearly so) symmetrical in this regard, which is why we still use the positive charge model.

In electronics, ground is usually just a "common" or "reference" connection. It may, or may not, be connected to earth ground.

For example, the negative side of a car battery is connected to the car body and that's called ground. If you connect a light bulb between +12V and the car body it will light-up. If you connect a light bulb between the +terminal of a car battery and earth ground, no current will flow and it will not light up. Or if you have 2 cars sitting side-by-side, a light bulb connected between +12V on one car and the body of the other car will not light-up.

It's quite common for a circuit to have both positive and negative power supplies. For example, an op-amp may operate from plus and minus 15V. You can measure +15V to ground or -15V to ground, and if you put your voltmeter between +15V and -15V, you will measure 30V.

If you simply connect a light bulb to a battery, there is no ground.

DVDdoug: In electronics, ground is usually just a "common" or "reference" connection. It may, or may not, be connected to earth ground.

For example, the negative side of a car battery is connected to the car body and that's called ground. If you connect a light bulb between +12V and the car body it will light-up. If you connect a light bulb between the +terminal of a car battery and earth ground, no current will flow and it will not light up. Or if you have 2 cars sitting side-by-side, a light bulb connected between +12V on one car and the body of the other car will not light-up.

It's quite common for a circuit to have both positive and negative power supplies. For example, an op-amp may operate from plus and minus 15V. You can measure +15V to ground or -15V to ground, and if you put your voltmeter between +15V and -15V, you will measure 30V.

If you simply connect a light bulb to a battery, there is no ground.

Basically, you as the engineer define a particular place as being 0V. Often, this is "Earth Ground" but like Doug said, sometimes you aren't connected to earth ground, so while calling your negative terminal on a battery "Ground" is technically wrong, but everyone understands anyways. As to how electrons flow, it is actually not all that direclty related, though it is useful for calculating voltage potentials and currents in different parts of a circuit. It is like defining your origin, but for voltages.

There appears for good cause for nothing to be more confusing to newcomers to electronics then with the words ground, common, circuit common, earth ground, negative voltage, positive voltage, negative ground, positive ground etc. It's amazing we ever get anything made to work. :D

. Add to that the ageless misconception of current flowing from positive to negative (they guessed in the early 1800s and got it wrong) Vs actual electron flow that we know and understand today. That ones still starts arguments today. :D

charged particles such as electrons move in response to a difference in electric potential, normally called "a voltage" or "potential difference". This means you always measure voltage between two points. An electron loses potential energy, not charge, when grounded (brought to the 0V reference point of your circuit). Charge is conserved always.

Compare with potential energy of a mass in a gravitational field - lifting an apple up increases its gravitational potential energy, dropping it releases it again, but the mass isn't affected (ignore Einstein for now).

Potential energy is best though of as being stored in the field, electric or gravitational.

We normally choose a convenient reference point for gravitational potential energy too, and call it "height = 0"

Hello,

I appreciate the reply but was wondering if you could clear up somethings for me?

DVDdoug: If you connect a light bulb between +12V and the car body it will light-up.

Is the phrase '+12V' referring to the negative terminal of the battery, because I assume that is where the electrons are physically flowing from.

DVDdoug: It's quite common for a circuit to have both positive and negative power supplies. For example, an op-amp may operate from plus and minus 15V. You can measure +15V to ground or -15V to ground, and if you put your voltmeter between +15V and -15V, you will measure 30V.

Could you elaborate on this further? Is a 'positive and negative power supply' the terminals of a battery and how can you have a -15V reading?

I guess my biggest and most unanswered query of them all is, on my battery terminal where it reads 'GND' and 'negative', is this where the electrons are ACTUALLY flowing from?

Thanks Again, All the replies have done a great job enhancing my understanding

I am aware that when an electron is grounded it loses its charge and reverts to a low energy state.

That's nonsense, right there.

michinyon: That's nonsense, right there.

Yes, my apologies- An electron cannot lose its negative charge, I am aware of that now

I guess my biggest and most unanswered query of them all is, on my battery terminal where it reads 'GND' and 'negative', is this where the electrons are ACTUALLY flowing from?

It matters not one little bit where the electrons are flowing from. But if you are curious they flow from the negitave to the positave terminals. If you have a battery marked ground and negitave then the ground is actually the positave battery terminal.

There is nothing in electronics where the direction of flow matters. Many beginners think this matters because they do not understand the nature of electricity. For example they are confused over why it does not matter what order to put a resistor and LED.

When scientists decided on the direction of current flow they did not guess but actually measured effects of ion flow in electrolysis.

Then why does the schematic symbol for a semiconductor diode have an arrow?

BTW: current does not flow, technically current is flow.

123Splat:
Then why does the schematic symbol for a semiconductor diode have an arrow?

DOH! I guess it is to show what end is the cathode and what the anode. It is certainly nothing to do with the direction of current.
I donâ€™t even see it as an arrow.

Now a transistor symbol does have an arrow to show what sort of transistor it is.

The actual flow of charge carriers can be in either direction depending on the majority charge carrier for the substance involved. But there is absolutely no need to know what that direction is in electronic engineering. We are not talking about condensed matter physics here.

A positive Power supply is a power supply that supplies a voltage potential positive to its reference point. A negative power supply supplies a voltage potential that is negative to a reference point. This reference point is what we call ground. Usually, a power supply is connected such that it's "common" or "ground" terminal is connected to the 0V Reference point. There is often little difference between a "positive" and "negative" power supply, depending on its make-up. If the supply is isolated, then it doesn't even matter and it can be either a positive or negative supply depending on how you hook it up. Non-isolated supplies you have to be more careful with.

And as a short answer to your question, from a physics aspect, Yes the electrons flow out of negative terminal of the supply. But like Grumpy Mike said, that isn't very relevant to electronics/electrical engineering, as it is just a sign convention. It is like defining your origin in physics.

I'm just surprised those electrons don't get dizzy in AC circuits, go this way, no go this way, make up your mind all ready, hey I'm flowing here, I'm flowing here.

'm just surprised those electrons don't get dizzy in AC circuits,

That is what they mean by "Electron Spin"

Drunken electrons...

That must explain the smoke.

This ain't helping Guptra much, sorry, but it has been fun!