I have started to learn the basics of electronics.
I have already studied what current, voltage and resistance is, but I seem to have some misunderstanding about how things work together.
I have a super simple circuit, which has a 6V power supply (battery pack), which has a 1.7V LED and a 330 Ohm resistor in parallel. (Imgur: The magic of the Internet)
I know how to select a resistor for a series led and resistor circuit, but I don't understand what happens to the current, when it flows trough both junctions.
I calculated that the total current in the circuit is 0.018A (6/330)
The current is supposed to split, right?
slipstick:
Why are you putting 6V directly across an LED which only wants 1.7V? Does that seem like a good idea?
The resistor should be IN SERIES with the LED so that it limits the current through the LED. NOT in parallel with it.
Steve
Does it mean that the resistor (when in parallel) does not affect the current, which flows trough the LED at all? Am I right?
So there will be 6A of current going trough the LED?
“Does it mean that the resistor (when in parallel) does not affect the current, which flows trough the LED at all?”
Correct.
“So there will be 6A of current going trough the LED?”
There will be much more than 6A going through the LED then when the smoke comes out and the plastic enters your eye the current will go to zero.
“Does it mean that the resistor (when in parallel) does not affect the current, which flows trough the LED at all?”
Correct.
“So there will be 6A of current going trough the LED?”
There will be much more than 6A going through the LED then when the smoke comes out and the plastic enters your eye the current will go to zero.
Alright, this makes things more clear.
But how can I calculate the total current and resistance in this circuit then?
You can't. The LED doesn't have a fixed resistance. In your circuit it basically shorts out the power supply. The current will be limited by the maximum current the supply can provide. And then the LED will go bang after which it has infinite resistance and it will take no more current.
I'm afraid it is basically a ridiculous circuit with no practical purpose.
The resistor still resists the current so to say - the current when given a choice will always take the path of least resistance, and that's not the resistor in that circuit. Well, a tiny amount of current will still flow through the resistor in reality but it's negligible. Until the LED pops, of course, assuming it fails open all current has to flow through the resistor.
Had you placed two resistors in parallel you would see current flow through both.
pupolajshu:
I have started to learn the basics of electronics.
I have already studied what current, voltage and resistance is, but I seem to have some misunderstanding about how things work together.
n00b Tips
Step #1 - know the Ohm's Law inside and out, backwards and forwards !
Step #2 - when dealing with LEDs, things are not quite as straightforward - try understanding various circuits with simple bulbs (incandescent = resistive loads) first.
pupolajshu:
I know how to select a resistor for a series led and resistor circuit, but I don't understand what happens to the current, when it flows trough both junctions.
That is covered by Kirchoff's Law.
Key tip that i wished i knew (fully understood) a lot earlier on my electronics journey - the device determines the current draw - NOT the power supply.
Connect them end to end ( series Circuit). It should work if you have not burned out the LED.
If the LED is good and it doesn't light, then turn the LED around. The resistor works either direction.
