Question from Code by Charles Petzold
Posted by Iguanas_Everywhere@reddit | learnprogramming | View on Reddit | 9 comments
Having a re-read of the first edition of this book, and there's just 1 sentence that's bugging me a bit, and has me questioning if I've followed correctly:
On pg 38, he says "So with the help of a couple of copper poles (or cold-water pipes), we can construct a two-way Morse code system with just two wires crossing the distance between your house and your friend's", and then there's a diagram showing a V connected (via the ground) to the bulb at your friend's house, and vice versa.
Isn't it actually 4 copper poles, rather than "a couple", in this case? The V represents a batter that is connected to the ground, no? So there's the two batteries both connected to the ground via the copper poles, and bulbs that are also connected to the ground via copper poles. Am I wrong?
teraflop@reddit
This is really an electronics/physics question, not a programming question, but anyway...
The "copper poles" the book is describing are the grounding rods. You only need one grounding rod at each end, and you can connect both the battery on the "sending" side and the light bulb on the "receiving" side to it.
Strange_Space_7458@reddit
Hey, at least we have someone who isn't asking how to motivate himself to get out of bed in the morning. I'll take it.
HealyUnit@reddit
this.bed.pop(this), clearlyinbetween-genders@reddit
Or asking us about Leetcode or Angela Yu.
Iguanas_Everywhere@reddit (OP)
Ah, ok that makes sense. V just means the battery is connected to the ground, but not necessarily to its own unique copper pole in the ground, it can share that pole with bulb, so to speak. Thanks!
And thanks for being cool with me asking the question here; there are quite a few threads about this book on this sub, so I figured it would fit. If there are other subs that you think are better suited to discussion of this book, just let me know your recommendations! :)
peterlinddk@reddit
No, it is only two wires. The V (I think it is intended to suggest "Voltage") represents the positive terminal of a battery with the negative terminal connected to ground.
It isn't that clear in the text, but it does say "You could replace the V with a battery with the negative terminal connected to ground", implicitly saying that the positive terminal is connected to the switch.
Every connection to the ground is the "same" ground - meaning that there is no need for an additional wire.
Iguanas_Everywhere@reddit (OP)
Yes, I agree about the two wires, but I'm questioning the "couple of copper poles" in the ground that he's referencing. The V is a battery connected to a copper pole in the ground, right?
peterlinddk@reddit
Yes, one side of the battery is connected to ground, but the other side is connected to the switch. The explanation on that page gets a bit muddy I agree, but on the previous page there is a drawing of a battery with the negative terminal connected to ground, and he writes: "I'm not going to draw this battery connected to the ground anymore. Instead I'm going to use the capital letter V", and then there drawing that matches the drawings on page 36 where he gradually removes the ground-wire.
I had to re-read the entire chapter to fully grasp what was meant by this last circuit - something that irks me a bit about that book (although I love almost everything else about it) is that it spends a lot of time making you understand something, and then too fast for me at least, removes it again, and now I just have to retain that knowledge in my head, and remember "ah yes, the ground is another connector, and every V-voltage-source is also connected (invisibly) to the ground on the other side!"
Strange_Space_7458@reddit
No the V's are batteries (1 each) and the copper poles are ground (1 each). Only two wires connect the houses.