When putting a Resistor in series with an LED

  • #1

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When putting an LED in series with a Resistor do you put it according to current convention (positive to negative) or to the actual current flow? Does it matter?
 

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  • #2
Borek
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What is the role of the resistor, and will its position in the circuit change the way it works?
 
  • #3
phinds
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When putting an LED in series with a Resistor do you put it according to current convention (positive to negative) or to the actual current flow? Does it matter?
The two diagrams you have shown are absolutely identical in every significant respect, and that would be true regardless of what element was in the place where you show the diode. If you don't understand that, then you seriously need to get back to basics before trying to go further.
 
  • #4
The two diagrams you have shown are absolutely identical in every significant respect, and that would be true regardless of what element was in the place where you show the diode. If you don't understand that, then you seriously need to get back to basics before trying to go further.
I have only studied Circuit Analysis with Resistor networks and now beginning to get into RC/RL Circuits so I don't really have an idea how circuits function in reality with my current knowledge, heck I don't even know fully what an LED is. This is something I google about out of my own spare time to understand more about circuits.

Anyways... But wouldn't you want the resistor being the first thing to take in the current BEFORE it hits the diode instead of AFTER it hits the diode?
 
  • #5
phinds
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I have only studied Circuit Analysis with Resistor networks and now beginning to get into RC/RL Circuits so I don't really have an idea how circuits function in reality with my current knowledge, heck I don't even know fully what an LED is. This is something I google about out of my own spare time to understand more about circuits.
Then I say again, you need to go back to basics. You are getting ahead of yourself and trying to learn in a very scatter-shot way. Not a good idea.

Anyways... But wouldn't you want the resistor being the first thing to take in the current BEFORE it hits the diode instead of AFTER it hits the diode?
When you get back to basics you will realize that it it utterly irrelevant and in fact your question doesn't even make any sense.. The current in a series circuit goes through everything at the same time.
 
  • #6
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You are trying to tackle speed-density engine maps without understanding that there are pistons going up and down inside...

Seriously, get a decent book (as recommended in your other thread) and start at the beginning. Voltage, current, charge, resistance... These concepts are deceptively simple and it’s tempting to skip over them quickly; however, they are the foundation of all your future studies. Learn them well; read different accounts from different authors; set out a piece of paper and pretend you’re explaining the concepts to someone else.

Otherwise you’ll end up like the narrator of a ‘science’ documentary I saw recently, who spoke of “4000 volts of direct current”.
 
  • #7
Borek
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Otherwise you’ll end up like the narrator of a ‘science’ documentary I saw recently, who spoke of “4000 volts of direct current”.
I just read a pop-sci book on biochemistry, where the author (PhD, professor in evolutionary biochemistry, so not some random person) claimed there is an electric field in the cell membranes reaching 30 MV/m* "as in a lightning".

*Haven't checked, but the number itself looks reasonable, something like a bit over 100 mV across membrane several molecules thick can yield this order of magnitude.
 
  • #8
574
273
I just read a pop-sci book on biochemistry, where the author (PhD, professor in evolutionary biochemistry, so not some random person) claimed there is an electric field in the cell membranes reaching 30 MV/m* "as in a lightning".

*Haven't checked, but the number itself looks reasonable, something like a bit over 100 mV across membrane several molecules thick can yield this order of magnitude.
Resting potential (difference) of a typical neuron is about 70 mV, across a membrane approx. 10 nm thick. This gives 7 MV/m. That’s given me a new appreciation of the dielectric properties of the phospholipid bilayer!
 

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