The book Practical Electronics by Scherz and Monk states (3rd ed., p 48):
A ground bus, or bus bar found in breadboards… serves as an adequate substitute for a single point ground.
Is this statement correct?
Electronic – Breadboards and ground loops
breadboardground
Related Solutions
Voltage is relative. One voltage level only makes sense if you have another voltage level to compare it to. If you would look at the signal wire alone you wouldn't get any wiser, you wouldn't measure a voltage. You need a reference to measure against, so that you can say that the signal is so-and-so-many volts, referenced to ground.
That referenced to ground is implied when we talk about voltage levels, unless otherwise indicated. Balanced signals are often symmetrical about ground, so that when on 1 wire the voltage goes to +1 V on the other wire it will go to -1 V. Nicely symmetrical. But the receiver won't look at one wire and see the +1 V; it will look at the voltage difference between the two wires, and then ground is not relevant. Such signals will most often be transmitted over twisted pair cables, where one wire is the positive signal and the other one the negative signal. There's no ground wire.
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Kortuk wants to see a pretty picture. Again. (sigh)
Et voilà, une jolie image. Don't look at En-Ya, this is about my wall clock. How high does it hang? Most people will say "about 2 meters". That's because we usually will take the floor as reference level, our "ground". But my apartment is on the second floor, and if I take street level as reference the clock will be at 8 m above street level. A geographer may suggest 35 m above sea level. So "height" has no meaning without a reference, and with voltage it's the same thing.
Where is that quote from? It is self-contradictory, and pretty much just plain wrong.
Current will flow if a load is connected between a generic power supply positive and negative, no ground connection is needed, unless you have some special purpose power supply.
A ground connection is often used for safety, especially in line non-isolated supplies, or as a means to reduce noise. Even so, not all supplies pass the ground on to the output terminals or even make it available (for common examples, think wall-warts and such with just a two pole output). Many supplies don't even have an incoming ground terminal from the mains (small switchers, and again, wall-warts).
I was going to post this as a comment, but it seemed to cover the question.
Edit as per comment below and corrected text.
Well, that does change things. Generally, a DC power supply has no output tied to ground, or connected to the supply electrically at all, so connecting a load between an output and earth ground would result in no current flow. Supplies that have an output set of terminals and a separate ground can often be configured (by jumping ground to one of the output terminals) as positive ground or negative ground if desired.
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Best Answer
No, the statement is not correct. A single point ground is used specifically to avoid daisy chained returns, because it addresses problems caused by them.
X is not an adequate substitute for Y, when Y is specifically designed to fix issues with X. At least, not in those circumstances when those issues are a problem.
If bussed returns were absolutely adequate, there would be no point in star grounding, because star grounding is more difficult to lay out and takes up more PCB space, and creates more messy point-to-point hookup cabling when it's done between devices in a chassis.
It is much more tidy to daisy chain devices. Imagine if every light in a Christmas tree had individual wiring all the way back to the power supply. But chaining, convenient though it may be, introduces parasitic interactions between circuits or devices. You can have a ground loop even on a single circuit board. For instance a the power output stage of an amplifier can generate large currents which can appear as a voltage on the reference ground of a sensitive input stage, because the return path happens to be shared.