As mentioned, The Art is very badly written for all purposes. May give some outcomes of tests or, some idea, but, the internet, usually, have better.
Someone said " node ". Well a node and intersection is the same thing : a dot, a point. Intersection is easier to understand.
I guess, the convicts are the only good writers, there. You must arrest more, to get better books, then.
That's deep...deep sh*t...
There are circuits depicted there that you're not able to find with google simply because you don't know their name or purpose...I had all 3 editions since 2009 and I wasn't able to draw such conclusions .
You miss and/or evade my point. It's not about the use of 'intersection' instead of 'node'. To me they are identical.
Read my post #13 again. I think that your understanding/explanation of Kirchhoff's current law is flawed.
I agree that is a more colloquial form of interpretation.
If you go on to solve a network, then you normally treat currents as entering a node from all related (i.e. connected) nodes. If currents flow out, the sign becomes negative, while currents flowing in are positive. Just the same as considering whether a battery is connected through a resistor with its positive or negative terminal "live" with the other grounded. That requires attaching a sign to the direction so that we know which way the current flows.
Simply put if your battery has one side grounded and you connect the resistor to the other terminal, then the current though it, from Ohm's law, will be positive if the voltage is positive or negative if the voltage is negative, with respect to the ground.
But are 'direction' and 'sign' in relation to a specific node not the same thing within the context of Kirchhoff's current law?
A current that is flowing towards a node has a positive sign, and its direction is towards that node. A current that is flowing away from a node has a negative sign, and its direction is away from the node.
Now imagine a neighbouring node, from which current is flowing towards the above node. The direction of that current is pointing away from that neighbouring node; it's sign is negative in relation to that neighbouring node. But the direction of this current is pointing towards the first node; it's sign is positive in relation to the first node.
TS writes (on page 23 of his Word document):
"However, on each intersection, one or all currents can be drawn to go the other way as long as the sign is changed. Thus, I1, which goes toward the intersection can be drawn to go away from the intersection, but, then, the current becomes - I1. The same applies for any current and voltage."
To me this looks like a 'double negative'. The direction is being changed, and the sign is being changed. So nothing really changes. What would be the purpose of that? To me it only makes things more difficult to grasp visually (some of the arrows pointing into the opposite direction of how current really flows).
The above doesn't change my critisism on what follows in the document of TS (still page 23 of his Word document):
"Thus, Kirchhoff says : The sum of all currents which go in the same direction to or from an intersection is zero. Thus, the sum of all currents which go in the direction, towards an intersection, is zero and the sum of all currents which go in the same direction, away from an intersection is zero."
To me this is just not true, unless atleast one of the currents involved has a negative sign (or unless all currents are 0, but than there are no 'signs' and 'directions'). But having a negative sign means that in reality that current has a direction pointing away from the node. For the staments to be true, the concept of the direction of eletrical current gets 'sacrified'. The part "...in the same direction..." in the statements of TS has no real meaning anymore, since atleast one of the currents in reality flows in the opposite direction (or all currents involved are 0).
Fully agree:
The sum of all currents which go in the same direction to or from an intersection is zero.
The sum of all currents that go in the same direction to a node is definitely, 100% sure NOT zero (unless each one of all those currents are zero to begin with).
This is just wrong, not semantics or whatever, plain wrong.
It's a no brainer. Take a node, and draw some currents with the SAME direction going to it. How in earth can the sum of those currents be zero?
Like +1A, +100mA, +1.22A. Sum = 1 + 0.1 + 1.22 = 0?? If you think otherwise you do definitely not understand Kirchoff.
Jan
The sum of all currents which go in the same direction to or from an intersection is zero.
The sum of all currents that go in the same direction to a node is definitely, 100% sure NOT zero (unless each one of all those currents are zero to begin with).
This is just wrong, not semantics or whatever, plain wrong.
It's a no brainer. Take a node, and draw some currents with the SAME direction going to it. How in earth can the sum of those currents be zero?
Like +1A, +100mA, +1.22A. Sum = 1 + 0.1 + 1.22 = 0?? If you think otherwise you do definitely not understand Kirchoff.
Jan
I did a couple of years of general engineering during my degree 20 years ago, and forgot much of the electronics, so over the past few years have been an avid reader on this forum and of 2nd hand old text books (including AofE) and online sources for general electronics, radio and audio stuff. I agree that the AofE isn't perfect, I found some other simpler texts were beneficial first, but it is good. That is the context in which I have had a quick glance through this word document. I might spend more time looking at it out of intrigue, but I have to say that if anything if shows how hard it is to write a good text for people to learn from. In parts it comes across as a learner's revision notes, and with some of the emphasis spent attempting to explain concepts that the author might have previously misunderstood, but which generally people probably don't have issues with. That said, I'll read the transistor section with a beer tonight...
I think that the word "direction" is what the TS is confused with. I suggest it is better to just consider current flow. Choose a sign convention like positive voltage to negative voltage is positive and define currents that way. "Sign" is also less relevant especially if actually solving a circuit. It seems to me that the TS maybe hasn't tried that, since the "need to know" really doesn't come into it.
If you take the view that ALL currents flow INTO a node, if they are subsequently found to have a negative sign, they're going (leaving) not coming (entering). The point is, this is mathematically how you would set up your problem. You don't know a priori whether to attach a positive or negative sign to a current, unless you already know or the circuit is simple and the answer is obvious, but even then I would not prejudge what signs to use.
I would add, in edit, that "direction" could be misleading since physically a current could be flowing in the same direction if entering from a higher voltage from the east while exiting to a lower voltage on the west". To me, "sign" is slightly better, but most importantly the actual sign of a current.
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IMO, it's very bad to move away from the commonly understood terms in electronics, physics or whatever. You lose the ability for people to clearly communicate, which is ultimately disastrous. Part of being knowledgeable in a field is understanding the terminology and basic concepts in the same fashion as everybody else.
Adding another take on some other comments to similar effect: The OP's choice of wording may be an attempt at describing the common practice when writing loop equations of assuming that all current loops flow in a particular direction (e.g. counterclockwise), with any currents flowing in the opposite direction then given a negative sign. In the OP's parlance, 'the same direction' may refer to the assumed direction of a current loop. That's the only way it made any sense to me, anyhow.
3a. An ideal bipolar transistor measures the current between the base and the emitter and adjusts the collector emitter resistance in such a way, so, the collector emitter current is, always, a coefficient B * the base emitter current. The coefficient B does not depend on currents and temperature.
3b. An ideal bipolar transistor is directionally oriented. Only NPN will be analysed. PNP is analogical.
You need to add
3c. No bipolar transistor is ideal.
First three lines under 3b are plain wrong and inconsistent with line 6. Lines 1 to 3 are not stand alone but at the very least need qualifying.
And if that is your premise that engineering can be reduced to simple logic, I am a little concerned. Engineering terms come about in order to give meaning to some physical phenomenon. A lot of simulation work goes into engineering which needs a little bit of maths. Trying to suggest otherwise is somewhat missing the point.
3b. An ideal bipolar transistor is directionally oriented. Only NPN will be analysed. PNP is analogical.
- No current can flow from emitter to base, regardless of voltages, currents, components, etcetera.
- No current can flow from collector to base, regardless of voltages, currents, components, etcetera.
- No current can flow from emitter to collector, regardless of voltages, currents, components, etcetera.
- The base emitter junction can be represented as an ideal diode from the base towards the emitter with forward voltage of 0V.
- The base collector junction can be represented as an ideal diode from the base towards the collector with forward voltage of 0V.
- The collector emitter junction can be represented as an ideal diode from the collector towards the emitter with forward voltage of 0V, when, the base emitter current * B is higher than the collector emitter current ( when fully open and in saturation ).
You need to add
3c. No bipolar transistor is ideal.
First three lines under 3b are plain wrong and inconsistent with line 6. Lines 1 to 3 are not stand alone but at the very least need qualifying.
And if that is your premise that engineering can be reduced to simple logic, I am a little concerned. Engineering terms come about in order to give meaning to some physical phenomenon. A lot of simulation work goes into engineering which needs a little bit of maths. Trying to suggest otherwise is somewhat missing the point.
Just beer......you'll need something much stronger to punch through a wall of barely comprehensible text.
Quote from the first page of this book:
Let's face it, why would anyone read or take anything seriously past this point, but then page 3 doubles down with:
Wasting your time with mathematics........well of course you have, page 4 says so:
Mathematics.........no thanks.......I'll use Algebra instead......it uses the alphabet:
Just a reminder of the branch of mathematics called RMS. It's mainly confusing because its half of something of a thing, then you half it again:
I'm worried to read past page 4 in the event I may never recover psychologically...............
I can assure you that the book continues in the same vein. I nearly stopped after the RMS confusion but had to take a peek at his transistor explanation. Everything is "simple" and the bipolar Vbe=0.65V, invariable, apparently. The guy hasn't even measured a bipolar from this gobbledegook. And temperature doesn't appear to be a problem in his world. So I don't think anyone can take this seriously. Or should not.
What is the RMS (root mean square) value of a quantity? It is a statistical quantity which cannot be understood without reference to numbers and operations like addition, multiplication, division and square rooting.
Refusing to use mathematics leads to guesswork, loss of time and damage to parts.
Refusing to use mathematics leads to guesswork, loss of time and damage to parts.