Electricity Theory Thread

[jenkinsontherun]

Thanks @SilverEars , I thought about that. I think there's just no way around reading textbooks, and building things.

https://www.amazon.com/G-Randy-Slone/e/B000APG19O?ref=dbs_a_def_rwt_bibl_vu00_i2 I might start with this.

Some tools I saw were Raspberry Pi, and these types of

gadgets.

Truth be told, I put off learning some of the stuff that I had set myself to learn, and time isn't an excuse. I think just gotta take it step by step. Not many people in their 20's want to set out and learn this stuff other than studying for an exam...so there's no example to follow. So really appreciate you guys giving advice for real.

Yea other than that, I don't expect you to give me much detail on what to buy to test out, although I would like to. A lot of this stuff can be googled, especially if it's just on what to buy. BUT a little advice won't hurt .

It seems just gotta go the hard way, get a textbook, spend time. No shortcut. But I will do it.

 

[SilverEars]

Thanks @SilverEars , I thought about that. I think there's just no way around reading textbooks, and building things.

https://www.amazon.com/G-Randy-Slone/e/B000APG19O?ref=dbs_a_def_rwt_bibl_vu00_i2 I might start with this.

Some tools I saw were Raspberry Pi, and these types of gadgets.

Truth be told, I put off learning some of the stuff that I had set myself to learn, and time isn't an excuse. I think just gotta take it step by step. Not many people in their 20's want to set out and learn this stuff other than studying for an exam...so there's no example to follow. So really appreciate you guys giving advice for real.

Yea other than that, I don't expect you to give me much detail on what to buy to test out, although I would like to. A lot of this stuff can be googled, especially if it's just on what to buy. BUT a little advice won't hurt .

It seems just gotta go the hard way, get a textbook, spend time. No shortcut. But I will do it.

You probably want to study analog circuits if relating to audio. Difference between self-learning and college is that, everybody are forced to learn in college, but self-learning is for people that are capable of absorbing information without the force. lol

Go to DIY forums for audio and learn to use multimeters and soldering iron and start building. It will make you want to figure out schematics and stuff. Somebody that builds a lot will know a lot from building stuff.

 

[Kentajalli]

pretty surprising find given what I assumed to be basic concepts

The above picture is worded wrongly, it confuses!
Voltage is the unit of measurement of Potential Difference (correct term) between two points, just like Meter is for measuring length, width or height.
You never say "if the legs of a table are at the same Meter, then it wouldn't wobble" Do you?
Equally the sentence "If both sides are at the same Voltage then ....." becomes wrong.
Voltage is measured between two points, it is sometimes falsely assumed that voltages are measured between ground and a point - that is a mistake!
To put the sentence correctly, it would be:
If the Potential difference between the ends of a light bulb is ZERO, then no current would flow!
Which would make it common sense, and leaves no room for confusion.
For fun, the bulb above has both ends at -ve few million volts! compared to black clouds on a stormy day - but so what?
Once something is described wrongly, then getting to the truth becomes difficult.

 

[jenkinsontherun]

The above picture is worded wrongly, it confuses!
Voltage is the unit of measurement of Potential Difference (correct term) between two points, just like Meter is for measuring length, width or height.
You never say "if the legs of a table are at the same Meter, then it wouldn't wobble" Do you?
Equally the sentence "If both sides are at the same Voltage then ....." becomes wrong.
Voltage is measured between two points, it is sometimes falsely assumed that voltages are measured between ground and a point - that is a mistake!
To put the sentence correctly, it would be:
If the Potential difference between the ends of a light bulb is ZERO, then no current would flow!
Which would make it common sense, and leaves no room for confusion.
For fun, the bulb above has both ends at -ve few million volts! compared to black clouds on a stormy day - but so what?
Once something is described wrongly, then getting to the truth becomes difficult.

Hi @Kentajalli . This is a response to your observation.

Follow advice from @SilverEars , I went and bought a kit, and built this a few days ago.

I will note some key things I learned while building this:
-Any device has its own resistance. I am relieved by this fact. Previously, I had thought that while batteries have a voltage (?), I was bugged by the mystery of how the current is discharged. For example, with such a low resistance from the wire, couldn't the battery explode from too much current being discharged? The answer is a no, because the battery has a resistance that controls the maximum current draw. I also learned about C rating, and batteries' lives (in mAh) depend on the current draw, higher average current draw means less battery life.

Now, this is the question:
How should I interpret the term voltage? Would it be correct to say: "Across the positive and negative terminals of the LED, there is a voltage drop"? I ask this, because in the tutorials, the instructors often say it like so. To me, it does make sense, even when using the length analogy as you related. I can say, "the leg of Sam's table is a meter longer than Pam's table."
Let's say that the multimeter measures a voltage drop (if I can say it like that) of 2V across the LED. Can I say that there is a potential difference of 2V across the LED?

I don't want to drag this longer as I am actually unsure of the terminology. In short, does voltage drop ===== potential difference, and similarly voltage rise ===== potential difference.

Edit: I believe it's more accurate to say voltage is potential difference than the above,

 

[pbui44]

Wow...it really looks like that $40/month that you offered for a tutor is really going to components alone.

 

[Kentajalli]

I am glad you are having fun with the kit, it is a great learning tool.
I am also proud of you to try to learn the theory too, many won't bother, and are just happy with flashing lights.
If you stick to correct definition of fundamentals, pieces just drop in their logical slots.
Example:
A diode Requires a certain voltage across it terminals, Before itit starts to conduct! (forward bias voltage)
This means the diode remains dead, untill a min. voltage is applied across its terminals (correct polarity ofcourse), then it switches on as though it was switch.
So voltage drop is sometimes used incorrectly, it applies to a resistor very well, but to a diode? not so much.
Always think of voltage as "water pressure difference" in a plumbing parallel world.
So voltage requires TWO points for it to be measured , because we are measuring difference between them - choose a wrong point, and your measurement would be meaningless.
So across the terminals of a diode, is the correct way - between one side and an arbitary point (e.g. ground) is wrong.
Going back to the wording on picture about ends of a light bulb, voltage at ends of the bulb being the same, becomes wrong, because each end on its own does not have a voltage, for it to be the same as the other side. If you put a volt-meter across the ends of the bulb, it would read zero! but both ends maybe at 1000V compared to a third arbitary point, but who cares?
In your LED experiment, 2 Volt potential difference across the terminals is correct - but keep in mind, the LED requires it before it starts to light up - give it more voltage and you can burn it out! Add a suitable resistor in series, and then you get voltage drop phenomena displayed in full glory.
- given 4 Volt supply, your voltmeter would read 2V across LED and 2V across resistor.
- given 6 Volt supply, across LED would remain at 2V but resistor now reads 4V.
- give it 10V supply , LED keeps reading 2V and resitor reads 8V!
Until you blow them up both, LED keeps reading 2V ! magic! but voltage drop across the resistor changes.
Have I lost you?

BTW - regarding the table, the heights of the table legs are not important - only the diffrence between the legs dictates, if it wobbles or not!
It would woblle at sea level, and on top of mount everest just the same, and the same amount.

 

[jenkinsontherun]

resistance is the inverse of conductance

 

[jenkinsontherun]

I am glad you are having fun with the kit, it is a great learning tool.
I am also proud of you to try to learn the theory too, many won't bother, and are just happy with flashing lights.
If you stick to correct definition of fundamentals, pieces just drop in their logical slots.
Example:
A diode Requires a certain voltage across it terminals, Before itit starts to conduct! (forward bias voltage)
This means the diode remains dead, untill a min. voltage is applied across its terminals (correct polarity ofcourse), then it switches on as though it was switch.
So voltage drop is sometimes used incorrectly, it applies to a resistor very well, but to a diode? not so much.
Always think of voltage as "water pressure difference" in a plumbing parallel world.
So voltage requires TWO points for it to be measured , because we are measuring difference between them - choose a wrong point, and your measurement would be meaningless.
So across the terminals of a diode, is the correct way - between one side and an arbitary point (e.g. ground) is wrong.
Going back to the wording on picture about ends of a light bulb, voltage at ends of the bulb being the same, becomes wrong, because each end on its own does not have a voltage, for it to be the same as the other side. If you put a volt-meter across the ends of the bulb, it would read zero! but both ends maybe at 1000V compared to a third arbitary point, but who cares?
In your LED experiment, 2 Volt potential difference across the terminals is correct - but keep in mind, the LED requires it before it starts to light up - give it more voltage and you can burn it out! Add a suitable resistor in series, and then you get voltage drop phenomena displayed in full glory.
- given 4 Volt supply, your voltmeter would read 2V across LED and 2V across resistor.
- given 6 Volt supply, across LED would remain at 2V but resistor now reads 4V.
- give it 10V supply , LED keeps reading 2V and resitor reads 8V!
Until you blow them up both, LED keeps reading 2V ! magic! but voltage drop across the resistor changes.
Have I lost you?

BTW - regarding the table, the heights of the table legs are not important - only the diffrence between the legs dictates, if it wobbles or not!
It would woblle at sea level, and on top of mount everest just the same, and the same amount.

Yes, in one of my online courses, two leds were placed in parallel. However, their colours were different. As a result of the ~0.6 min. voltage requirement difference, one LED actually doesn't light up!

However, when I think about this a bit further, how can two LEDs light up, even if they are the same color? After all, manufacturing them produces unit variation. So, if one is 1.9V, and the other is 2V, will it still work? What topic explains, or "debunks," this thought? Thanks!

 

[Kentajalli]

Yes, in one of my online courses, two leds were placed in parallel. However, their colours were different. As a result of the ~0.6 min. voltage requirement difference, one LED actually doesn't light up!

However, when I think about this a bit further, how can two LEDs light up, even if they are the same color? After all, manufacturing them produces unit variation. So, if one is 1.9V, and the other is 2V, will it still work? What topic explains, or "debunks," this thought? Thanks!

The color of the LED determines, what junction material is used and what forward voltage is required.
The diffrence between the forward voltages is not because of manufacturing glitches.
Colour has a frequency, just like sound, it is much higher but there is a frequency.
The lower the frequency the more RED the light is, higher frequencies push the colour towards BLUE.
Say Red is Bass, Blue is treble !
When a certain diode junction material is exposed to a voltage, as the voltage approaches the forward voltage, electrons start to jump from one side of the junction to the other - also photons start to emit at a certain frequency which is natural to the materials used, this frequenct dictates the colur.
You know, copper burns green, sodium burns yellow - similar phenomena.
Now if you give it more voltage, more photons are emitted, but at the same colour, so the LED gets brighter only.
Multicolour leds are actually a few leds connected in parallel. - think about it - a green led connected to a red led but in reverse polarity - give it forward voltage, the green lights up, reverse the voltage, it becomes red, give it AC ! and it cycles through red and green, so it would seem yellow !

 

[jenkinsontherun]

I am glad you are having fun with the kit, it is a great learning tool.
I am also proud of you to try to learn the theory too, many won't bother, and are just happy with flashing lights.
If you stick to correct definition of fundamentals, pieces just drop in their logical slots.
Example:
A diode Requires a certain voltage across it terminals, Before itit starts to conduct! (forward bias voltage)
This means the diode remains dead, untill a min. voltage is applied across its terminals (correct polarity ofcourse), then it switches on as though it was switch.
So voltage drop is sometimes used incorrectly, it applies to a resistor very well, but to a diode? not so much.
Always think of voltage as "water pressure difference" in a plumbing parallel world.
So voltage requires TWO points for it to be measured , because we are measuring difference between them - choose a wrong point, and your measurement would be meaningless.
So across the terminals of a diode, is the correct way - between one side and an arbitary point (e.g. ground) is wrong.
Going back to the wording on picture about ends of a light bulb, voltage at ends of the bulb being the same, becomes wrong, because each end on its own does not have a voltage, for it to be the same as the other side. If you put a volt-meter across the ends of the bulb, it would read zero! but both ends maybe at 1000V compared to a third arbitary point, but who cares?
In your LED experiment, 2 Volt potential difference across the terminals is correct - but keep in mind, the LED requires it before it starts to light up - give it more voltage and you can burn it out! Add a suitable resistor in series, and then you get voltage drop phenomena displayed in full glory.
- given 4 Volt supply, your voltmeter would read 2V across LED and 2V across resistor.
- given 6 Volt supply, across LED would remain at 2V but resistor now reads 4V.
- give it 10V supply , LED keeps reading 2V and resitor reads 8V!
Until you blow them up both, LED keeps reading 2V ! magic! but voltage drop across the resistor changes.
Have I lost you?

BTW - regarding the table, the heights of the table legs are not important - only the diffrence between the legs dictates, if it wobbles or not!
It would woblle at sea level, and on top of mount everest just the same, and the same amount.

So the phrase "voltage drop" does make sense.

This post is just fleshing out a thought, not raising any more questions (hopefully).

At an area on the wire just before the resistor, the voltage is zero, assuming the wire has no resistance. By voltage=zero I mean two points on the wire very close to each other, as you say that a voltage measurement from a random point doesn't make any sense. So I choose two points close to each other on the wire as voltage=zero. Small detail.

Measuring between the two terminals of the resistor, the voltage is negative-something.

We went from 0 voltage to negative-something, so we can say it's a voltage drop. 0->-2 is clearly a drop.

Originally I still had a bit of trouble grasping the "difference" concept. However, a difference is just a number after all.


So in fact a voltage drop by implication refers to 4 points on the circuit.

 

[Kentajalli]

So the phrase "voltage drop" does make sense.

This post is just fleshing out a thought, not raising any more questions (hopefully).

At an area on the wire just before the resistor, the voltage is zero, assuming the wire has no resistance. By voltage=zero I mean two points on the wire very close to each other, as you say that a voltage measurement from a random point doesn't make any sense. So I choose two points close to each other on the wire as voltage=zero. Small detail.

Measuring between the two terminals of the resistor, the voltage is negative-something.

We went from 0 voltage to negative-something, so we can say it's a voltage drop. 0->-2 is clearly a drop.

Originally I still had a bit of trouble grasping the "difference" concept. However, a difference is just a number after all.


So in fact a voltage drop by implication refers to 4 points on the circuit.

Remember the word drop is not meant as lower, or coming down say from 0 to -4V.
It is better to assume the word drop as appear.
In better terms, when they say a voltage drop of 4V, it means a 4V voltage appearance!
I'll try to explain.
There are different ways to look at current, voltage and resistance phenomena. Ohm's law V=IxR explains the relationship.
- so if a voltage of 4V is applied across a 2 ohm resistor, a current of 2 amps would flow as a result.
- OR ! if a current of 2 amps should flow through a 2 ohm resistor, the a voltage difference appears or is dropped across the resistor.
This appearance of voltage across a resistor is referred to as voltage drop!
the direction of the flow of current determines the -ve or +ve attribute otherwise -4V or +4V is just a matter of point of view.
So in no way drop is meant as lower.
This term is used when in a circuit we know the amount of current flow, and we need to calculate (or manipulate) the voltage.
In some circuits we may have constant current, so we can calculate various voltage drops across different resitors.
Let us take your LED circuit for example.

One can say Point A is at (say) 1V and point B is at 3V so voltage drop across the LED is 2V.
However, a lot of assumptions are included in that statement.
Point A is at 1V if measured with reference to Ground point, equally point B is at 3V with reference to Ground point again.
What if we did not know where Ground point was? it can happen!
In a complex circuit with multiple voltage sources, interconnected, the ground point may not be at a proverbial 0V.
What if we ignore this ground point - the points A and B would become just two points on our circuit, connect a voltmeter across them to measure your 2Volts.
Equally if Point B is indeed at 3V and the battery is a 6V supply, if R1=100ohms then current is I=0.03A according to ohms law. (30mA) equally same current flows through R2, that make R2 with a voltage drop if 1V to be 33.3 ohms.
This is what voltage drop is, and how it is used.
The same argument is not valid across the LED - because eventhough we have 2V across it, the LED is not a resistor, so Ohms law does not directly apply.
Did I make things clearer or more cloudy?

 

[jenkinsontherun]

Remember the word drop is not meant as lower, or coming down say from 0 to -4V.
It is better to assume the word drop as appear.
In better terms, when they say a voltage drop of 4V, it means a 4V voltage appearance!
I'll try to explain.
There are different ways to look at current, voltage and resistance phenomena. Ohm's law V=IxR explains the relationship.
- so if a voltage of 4V is applied across a 2 ohm resistor, a current of 2 amps would flow as a result.
- OR ! if a current of 2 amps should flow through a 2 ohm resistor, the a voltage difference appears or is dropped across the resistor.
This appearance of voltage across a resistor is referred to as voltage drop!
the direction of the flow of current determines the -ve or +ve attribute otherwise -4V or +4V is just a matter of point of view.
So in no way drop is meant as lower.
This term is used when in a circuit we know the amount of current flow, and we need to calculate (or manipulate) the voltage.
In some circuits we may have constant current, so we can calculate various voltage drops across different resitors.
Let us take your LED circuit for example.

One can say Point A is at (say) 1V and point B is at 3V so voltage drop across the LED is 2V.
However, a lot of assumptions are included in that statement.
Point A is at 1V if measured with reference to Ground point, equally point B is at 3V with reference to Ground point again.
What if we did not know where Ground point was? it can happen!
In a complex circuit with multiple voltage sources, interconnected, the ground point may not be at a proverbial 0V.
What if we ignore this ground point - the points A and B would become just two points on our circuit, connect a voltmeter across them to measure your 2Volts.
Equally if Point B is indeed at 3V and the battery is a 6V supply, if R1=100ohms then current is I=0.03A according to ohms law. (30mA) equally same current flows through R2, that make R2 with a voltage drop if 1V to be 33.3 ohms.
This is what voltage drop is, and how it is used.
The same argument is not valid across the LED - because eventhough we have 2V across it, the LED is not a resistor, so Ohms law does not directly apply.
Did I make things clearer or more cloudy?

Thanks for this. going to take some time to digest it.

 

[SilverEars]

Remember the word drop is not meant as lower, or coming down say from 0 to -4V.
It is better to assume the word drop as appear.
In better terms, when they say a voltage drop of 4V, it means a 4V voltage appearance!
I'll try to explain.
There are different ways to look at current, voltage and resistance phenomena. Ohm's law V=IxR explains the relationship.
- so if a voltage of 4V is applied across a 2 ohm resistor, a current of 2 amps would flow as a result.
- OR ! if a current of 2 amps should flow through a 2 ohm resistor, the a voltage difference appears or is dropped across the resistor.
This appearance of voltage across a resistor is referred to as voltage drop!
the direction of the flow of current determines the -ve or +ve attribute otherwise -4V or +4V is just a matter of point of view.
So in no way drop is meant as lower.
This term is used when in a circuit we know the amount of current flow, and we need to calculate (or manipulate) the voltage.
In some circuits we may have constant current, so we can calculate various voltage drops across different resitors.
Let us take your LED circuit for example.

One can say Point A is at (say) 1V and point B is at 3V so voltage drop across the LED is 2V.
However, a lot of assumptions are included in that statement.
Point A is at 1V if measured with reference to Ground point, equally point B is at 3V with reference to Ground point again.
What if we did not know where Ground point was? it can happen!
In a complex circuit with multiple voltage sources, interconnected, the ground point may not be at a proverbial 0V.
What if we ignore this ground point - the points A and B would become just two points on our circuit, connect a voltmeter across them to measure your 2Volts.
Equally if Point B is indeed at 3V and the battery is a 6V supply, if R1=100ohms then current is I=0.03A according to ohms law. (30mA) equally same current flows through R2, that make R2 with a voltage drop if 1V to be 33.3 ohms.
This is what voltage drop is, and how it is used.
The same argument is not valid across the LED - because eventhough we have 2V across it, the LED is not a resistor, so Ohms law does not directly apply.
Did I make things clearer or more cloudy?

Actually I think of 'drop' as dropping the voltage through the component (resistor), and therefore the voltage is dropped in a series (closed circuit or loop), because the voltages will drop on the components in the series, and supply voltage being split between them based on the resistance value ratio among the components, thus each component having different voltage drops ( due to the ratio ) of the supply voltage. For parallel, same voltage dropped each per line of the split in parallel, and if any of the loop in parallel has series connected components, ratio rule applies for each loop (and sums to supply voltage).

If a voltage supply makes a loop with components in the loop, total voltage from the supply is dropped on those components (per loop if there is parallel) from the supply.

If you do enough of the problem they provide in the text books, you realize it's just simple ratios. Or think of it as a proportion of a pie, and each component taking part of the voltage supply pie. The point of understand these concepts is when you can see it so simply. Students solving problems doesn't mean they understand it. Until they can see it being really simple ratios of components in each loop.

 

[jenkinsontherun]

Hey guys, been a bit busy lately. Thanks for both your answers @SilverEars @Kentajalli .

Now, I do plan to look into your explanations deeper.

However, after skimming through both answers, it seems that both explanations makes sense.

@Kentajalli 's answer is very coherent with the water pressure analogy. I can imagine placing a windmill-type structure in flowing water, and water pressure "appears" at this location. Just as we put resistor in a circuit, pressure, or volts, appears.

@SilverEars answer also makes sense, and is perhaps more "science class" type explanation which is of course okay.

No more questions now. I will take some time to look over both answers, and really develop an understanding of the terminology, as well as how it works.

 

[Kentajalli]

and really develop an understanding of the terminology, as well as how it works.

AAh, Terminology!
Here you have touched on a big issue.
We as humans have observed the physical world in which we live in, and tried to decypher its inner workings - in the hope to discover the rules under which this world operates, so we can manipulate, alter or recreate parts of it to our advantage.
At the very early stages of this study, observation (call it what you may) it was fast realized that our standard language (English, Arabic, Greek) is not sufficient for such a task.
Quickly it was realized that the only language suitable is Mathematics.
But not everybody is fluent in Maths - so certain terminology was adopted to describe phenomena, in order for others to understand findings of scientists before them to further the study.
Certain terminology was adopted from a certain vantage view of the scientists of the time in their language - some got translated into different languages, some very badly!
Bottom line, drop maynot mean drop, potential may have a different meaning and so on - why? because the only valid language to explain the physical universe is Mathematics! the rest are best approximations.
Reading text books without a guide, can be confusing.