I am making a heated blanket and I have some troubles to determine the heat that will be generated.
Resistance: Let say, I use this heated cable with a resistance of 0.3 Ohms/m*. If I am using 10m of this cable the resistance will be 3 ohms.
Voltage: I will use a AC adaptator with a voltage of 19V.
Current: So the current that will be drawed is 19/3 = 6.3A
But my adaptator delivers a current of 3.16A, so which current should I use to determine the Watts that my blanket will output? 3.16A or 6.3A?
My guess is that it will be limited to 3.16A but that's where I get confuse because it seems that the length of the cable doesn't count anynore (if it's below 20m) :
a 1 m cable should draw 63.3A (at 19v and 0.3 ohms/m) but with a input current of 3.16A, it should only draw 3.16A.
a 15 m cable should draw 4.22A (at 19v and 0.3 ohms/m) but with a input current of 3.16A, it should only draw 3.16A.
a 20 m cable should draw 3.16A (at 19v and 0.3 ohms/m) but with a input current of 3.16A, it should only draw 3.16A.
a 30 m cable should draw 2.11A (at 19v and 0.3 ohms/m) but with a input current of 3.16A, it should only draw 2.11A.
This seems to mean that A 1m cable or a 20m cable will generate the exact same heat but a cable longer than 20m will start to generate less heat.
Could that be correct because it doesn't make sense to me and I can't find where is my reasoning mistake.
Thanks a lot for shedding some light on this!
*I could only find the resistance per m of this cable on a forum. But for all the other cables I looked for, I've never found the resistance/m. Why the sellers never give this info? It is a specification too obvious to notify?