Electronics > Beginners
Using a small resistor in some water instead of a power resistor?
Zero999:
--- Quote from: help_me_pick_username on November 03, 2019, 01:28:25 am ---
--- Quote from: schmitt trigger on November 02, 2019, 10:57:19 pm ---This can easily become Photonicinduction - worthy experiment.
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What's photoinduction?
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He was a crazy Youtuber who used to blow stuff up with high voltages.
--- Quote from: help_me_pick_username on November 02, 2019, 10:08:46 pm ---
--- Quote from: MLXXXp on November 02, 2019, 09:31:15 pm ---Do you have more than one 1/4 watt resistor of the value you need? If you have 4 of them, you can series/parallel them to make a 1 watt equivalent. You can do the same with more, and even use multiples or fractions of the value, to get as much power handling as you need.
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I should have more than one... however, isn't there this thing when you put multiple resistors in parallel, the current will just go through the one that has the least resistance...? I only have 5% precision, so this could be an issue, right?
I can always do series though... Thanks for the suggestion!
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Yes, connecting resistors in parallel causes most of the current to go through the one with the least resistance.
Note that he said series in parallel. Suppose you have four, 1 Ohm resistors. Connect a pair of them of them in parallel, to make 1/2Ohm, now connect another pair in parallel to get another 1/2Ohm, put them in series and you now have a 1Ohm resistor with four times the power rating. You could also put two series pairs of 1R resistors in parallel: the effect would be the same: 1Ohm at four times the power.
Don't worry about the tolerances. Some of the resistors will be above an Ohm and others below, so it won't make and difference. In fact, the resulting resistor will have a greater precision, than each resistor, as the errors average out to some degree.
Siwastaja:
--- Quote from: Zero999 on November 03, 2019, 10:59:24 am ---Yes, connecting resistors in parallel cause the current to go through the one with the least resistance.
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No, never say this. I know it gets stuck: it's a very common lie that is taught to us early on (speaking of Youtubers, I think Electroboom had a section about it on some of his videos). It has no merit in reality, not even as a simplification, because it is clearly just plainly wrong, and won't provide useful abstraction for any practical use.
I know you know what you are talking about, but phrases like this are extremely confusing, and the beginners must unlearn such widely touted lies.
Your words are clear: "the current" "through the one". This is just plainly wrong. Correctly would be, more current goes through the smaller resistance.
Of course, our complete electrical system is a bunch of things connected in parallel - classically even simple resistances, such as heaters. We all know that turning on a heater does not much affect the others.
You are right that tolerances are indeed not that meaningful, but this goes for both parallel and serial connections, so use whichever is easier for the particular set of resistor you have, and based on the ease of making the actual connections physically.
Unless the tolerances are really crappy, or the system is improperly dimensioned to be really on the edge without any margin whatsoever...
Zero999:
--- Quote from: Siwastaja on November 03, 2019, 12:44:41 pm ---
--- Quote from: Zero999 on November 03, 2019, 10:59:24 am ---Yes, connecting resistors in parallel cause the current to go through the one with the least resistance.
--- End quote ---
No, never say this. I know it gets stuck: it's a very common lie that is taught to us early on (speaking of Youtubers, I think Electroboom had a section about it on some of his videos). It has no merit in reality, not even as a simplification, because it is clearly just plainly wrong, and won't provide useful abstraction for any practical use.
I know you know what you are talking about, but phrases like this are extremely confusing, and the beginners must unlearn such widely touted lies.
Your words are clear: "the current" "through the one". This is just plainly wrong. Correctly would be, more current goes through the smaller resistance.
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I appreciate the correction, but resent your implication of lying. It was a simple mistake. I omitted the words "most of". I've edited my post. Don't be so quick to accuse others of dishonesty.
m3vuv:
why water and not oil??
Siwastaja:
--- Quote from: Zero999 on November 03, 2019, 06:47:34 pm ---I appreciate the correction, but resent your implication of lying. It was a simple mistake. I omitted the words "most of". I've edited my post. Don't be so quick to accuse others of dishonesty.
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Oh, I mean all the textbooks saying this are lying; this is where it gets stuck to our language from. Doesn't require active "lying" on your part, this wasn't intended. It just comes "automatically", I have said that too.
The authors of such textbooks may even know their stuff, but think that conceptually, a "convenient" lie is always a good idea, as a simplification. Sometimes it is, but it goes too far in this case. Hence, lying.
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