In your example with the LED it has to be calculated backward. The LED will have 2V across it (actually not in this case due to a high resistor value) and so the resistor will have 7 and so the current that will flow is I=V/R = 7/3300000 = 0.000002 Amps. I think you may have the wrong resistor value, a normal value for this example would be more like 330Ω.
Mike.
The quick answer is that it would still be 3.82 volts.So if I had a 6v and used a 3.3k what would be voltage dropped to after 3.3k resistor?
&*%^#$% keyboard!!!
What you have here is a very poor example for learning "Ohms Law".
At the risk of the thread turning into a blood bath, I will state that devices like LEDs, diodes and transistors do not obey Ohms Law.
(There has been a lot of heated debate about this in the past!)
The quick answer is that it would still be 3.82 volts.
LEDs have a nearly constant voltage drop arcoss them which varies by only a small amount when the current through them varies.
If you set your meter to measure current, in your original circuit you should see that the current is (8.7 - 3.82)/3300 = 1.48mA or maybe a bit less because the meter will add resistance to the circuit, making the current a bit smaller.
When you use a 6v battery, the current will be (6 - 3.82)/3300 = 0.66mA. Depending on the LED, it may not be very bright at this low current.
JimB
Well, Ohm's Law does apply but not in the usual manner. The LED's resistance isn't fixed, it changes in order to maintain a fixed voltage. Resistors are fixed, a 1k resistor will always be 1k regardless of the voltage placed across it (tolerances and thermal characteristics excluded). Increase the voltage, and the current increases, as does the voltage across the resistor.The problem here is that ohms law doesn't apply to LEDs. LEDs will have (generally) 2V across them unless the current is very low as in your case.
I think for simplicity's sake we need to avoid specifics like this while someone is trying to wrap their mind around a basic concept such as Ohm's and Kirchoff's laws. It doesn't sound like the OP is at the stage where he or his son is ready for that.
I was thinking we should avoid things like Kirchoff, Thevenin and Norton (from your earlier post).
Mike.
I was thinking we should avoid things like Kirchoff, Thevenin and Norton (from your earlier post).
Mike.
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