Ground symbol (code by Charles Petzold)

Hi guys,

currently reading code by Charles Petzold,

on chapter 5, he mentions words such as common and ground but I can't figure out what they do and how they relate to circuitry,

and mainly I don't understand the ground symbol he uses and not sure what context he uses it in.

If anyone has read this book and knows the chapter I'm referencing, would be great top hear your input,

Thanks!
Do you mean symbols like the ones shown here?
https://en.wikipedia.org/wiki/Ground_(electricity)#Electronics

Anyway, I probably don't have it, but what's the ISBN of the book?
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yep, the earth ground symbol in the link, I'm not sure how it functions in regards to computer circuits or circuits in general, I've tried watching a couple of tutorials but they seem to go over my head.

978-0735605053 is the ISBN
ground absorbs (removes) all the power ... do you know anything at all, like in practice how you put jumper cables to a grounded part of the vehicle, or how 3 prong outlets use ground and why they are safer?

Computer circuits are described in two flavors ... there is the actual electrical work, and there is the logic gate work. the real circuits do make the logic gates, but when looking at how to add two integers, you usually only look at the logical side until you grasp that. The circuit has a lot more doo-dads in it than the logical version and is harder to understand how the addition works with all the other stuff going on, so they split it out to look at the logic apart from the electronics. I don't know what you are trying to understand, but most computer programming books should not have a lot to say about grounding a circuit :) A computer engineering or electronics engineering book would have those things.
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Electricity, crudely analogous to water, flows through electronics at a particular rate ("current") and under a particular pressure ("voltage"), generated by a pump or "source" (e.g., a battery). As the energy in flowing water might be used to turn a water wheel, the energy transmitted by the flow of electrons can be used to turn on the lights or do some computation.

Water pumped through the system must eventually return to the pump. A fountain in a pond is example -- as long as it doesn't lose too much water. But it works for any faucet, too: the water cycle and/or your city's infrastructure will eventually move the water back to the pump station.

This is why "circuits" are so named: they contain cycles through which electrons flow.

"Common" is just a name for a (shared) part of the circuit used for returning to the source. It's a single return pipe to the pump.

Earth, ground, common, etc., can be collectively called "ground". Each essentially has the same purpose - to return current to the pump. The difference is that the pressure in each might differ; there may be a nonzero voltage differential or electric potential between them.

Most components within a system should be connected to the same ground. Otherwise the pressure differential between the different grounds may cause undesirable current to flow. When this happens by accident, it's called a ground loop, a major source of hum and interference in consumer products, and blown-up instrumentation in circuit design.
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ground absorbs (removes) all the power ... do you know anything at all, like in practice how you put jumper cables to a grounded part of the vehicle, or how 3 prong outlets use ground and why they are safer?


@ Jonnin Not much when it comes to electronics to be honest, I know a little about what voltage,wattage,current,amps are and have a rudimentary understanding of how electrons move from one atom to another( this happens with conductive materials such as metals ), but so far that's about it haha

@ mbozzi, great analogy, that's a little clearer now :)

in the book Charles mentions :

when you find a common part of a circuit, you can remove the wires and use the earth instead of a wire, let me actually link a copy of the actual problem from the book - https://ibb.co/MVqrBMH

A) I'm not sure how a common reduces the number of wires involved

B) I'm not even sure what is meant by common in this regards

and C) I'm not sure how common in this context relates to the ground or sending the connection through (literally using) the ground.
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I have not looked at this stuff in 30 years, but -- it seems likely to mean this:
common maybe short for 'common ground' which you can also think of as just 'ground'.

if so, it reduces wires -- could be that you just directly tap from where you are out to something. Back to the simple example of jumper cables, you attach one to the car body, anything large and metal, as 'ground'. Could also be you make a short hop to a long common wire, rather than route a bunch of wires back around to the battery. I honestly do not know what they do on printed circuit boards. At some point you are going to tie back into the power supply and its third prong 'ground' wire, but the details beyond that are more than I understand.

the reason it is called 'ground' is that in early study, it was literally a bar or wire driven into the dirt. That is still done -- when I was growing up our TV antenna (look it up) was the highest point on the home and so it had a thick wire driven into the ground in case it was hit my lightning. Lightning also is seeking 'ground' -- its a high positive charge with nowhere to go until it finally gets strong enough to jump the gap to then negative terminal (the earth).

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When you find a common part of a circuit, you can remove the wires and use the earth instead of a wire, let me actually link a copy of the actual problem from the book - https://ibb.co/MVqrBMH


Ground is a generic term. All "grounds" (the actual planet Earth, the metal chassis of an instrument, a common ground wire), all have the same purpose: they're intended as a return path for current back to the source.

Not all grounds are equal, but their purpose is the same - to allow current to return. In the case of the picture, the black wire is common. When exactly one switch is closed, current will flow through the light bulb and return to the originating cell via the black wire.

Back to the simple example of jumper cables, you attach one to the car body, anything large and metal, as 'ground'.

The chassis of the car has a direct connection to the negative terminal of the battery. This saves on wire because some devices don't need a dedicated wire to return current - they can use the chassis for this purpose.
See:
https://en.wikipedia.org/wiki/Single-wire_earth_return

P.S.: You can clamp red-to-red and black-to-black on both vehicles, but this isn't done for safety reasons. Dead lead acid batteries can off-gas hydrogen.

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