When I connect an LED and an Ammeter serial to a 9V battery, the Ammeter shows 13.2 kA. If I add a 1 microOhms resistor serial to the rest, the Ammeter shows 4.06 MA. Also the LED has 1.29V between each side and the resistor has 4.06V which doesn't add up to 9V.
I tried to tweak the LED but the properties I can adjust are breakdown voltage, color, emission coefficent and saturation current none of which seems to change the readings on anything.
Normally a 9V battery, a standard LED and a 300 Ohms resistor would work in a way that the circuit has around 20 A and the voltage is more or less evenly distributed to the resistor and the LED.
So what am I doing wrong here? I don't understand.
When I connect an LED and an Ammeter serial to a 9V battery, the Ammeter
shows 13.2 kA. If I add a 1 nanoOhms resistor serial to the rest, the
Ammeter shows 4.06 MA. Also the LED has 1.29V between each side and the
resistor has 4.06V which doesn't add up to 9V.
A battery has an internal resistance and this should be what you're seeing
here. I don't have a working installation of ktechlab but there should be a
way to tweak the resistance or maybe an ideal voltage source you can use
instead of the battery.
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Also when I think about it, the total resitance on the circuit is so small that the ammeter's resistance may have been taken into account. However that is the least of the problems I have. The main thing that concerns me is that the led has next to zero resistance. This almost makes sense to me since it's a diode but I don't think that is the case with real LEDs
Last edit: timucin 2017-05-28
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Turns out LEDs do have a voltage drop but not a constant resistance like resistors. Instead they tend to keep the voltage drop stable.
That's the reason when the resistor is 1 microOhm the LED also seems to have almost no resistance and the total Resistance becomes so small that the Ammeter has a noticable voltage drop and the current is bigger than the one with only one LED.
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You are correct, the LED (and Diodes, in general), does not have constant resistance. In the example circuit you are practically connecting in parallel two components with try to keep a constant, but different voltages on them.
In a real-world circuit, either the LED or the voltage source/battery would get burned.
Please note that for such extreme cases (when you see Mega-Ampers or Mega-Volts or higher in the circuit), probably ktechlab does not simulate the circuit accurately.
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
When I connect an LED and an Ammeter serial to a 9V battery, the Ammeter shows 13.2 kA. If I add a 1 microOhms resistor serial to the rest, the Ammeter shows 4.06 MA. Also the LED has 1.29V between each side and the resistor has 4.06V which doesn't add up to 9V.
I tried to tweak the LED but the properties I can adjust are breakdown voltage, color, emission coefficent and saturation current none of which seems to change the readings on anything.
Normally a 9V battery, a standard LED and a 300 Ohms resistor would work in a way that the circuit has around 20 A and the voltage is more or less evenly distributed to the resistor and the LED.
So what am I doing wrong here? I don't understand.
Here is the file I saved:
Last edit: timucin 2017-05-28
2017-05-28 18:01 GMT+02:00 timucin toraman@users.sf.net:
Also when I think about it, the total resitance on the circuit is so small that the ammeter's resistance may have been taken into account. However that is the least of the problems I have. The main thing that concerns me is that the led has next to zero resistance. This almost makes sense to me since it's a diode but I don't think that is the case with real LEDs
Last edit: timucin 2017-05-28
In case anyone else is having the same confusion I found an explanation for this.
https://electronics.stackexchange.com/questions/76367/accounting-for-led-resistance/76372#76372?newreg=ae8bec16116449b38b8b3f548d004072
Turns out LEDs do have a voltage drop but not a constant resistance like resistors. Instead they tend to keep the voltage drop stable.
That's the reason when the resistor is 1 microOhm the LED also seems to have almost no resistance and the total Resistance becomes so small that the Ammeter has a noticable voltage drop and the current is bigger than the one with only one LED.
You are correct, the LED (and Diodes, in general), does not have constant resistance. In the example circuit you are practically connecting in parallel two components with try to keep a constant, but different voltages on them.
In a real-world circuit, either the LED or the voltage source/battery would get burned.
Please note that for such extreme cases (when you see Mega-Ampers or Mega-Volts or higher in the circuit), probably ktechlab does not simulate the circuit accurately.