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Lets say we have a 12V power source connected to a single load, and 2.4 amps go through this wire. The wire will heat up.

Now the same 12V source, but now there’s two loads, each pulling 1.2 amps each. Which will heat the wire more? Would each node absorb half of the heat? Assume we’re using roughly the same length of wire for each circuit. Like this:

enter image description here

My guess is that the heat will transfer through both nodes, resulting in the same temperature as if with just one single load.. And some background: This question came up during a discussion about breadboard power rails and pulling too much current through them.

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    \$\begingroup\$ You probably meant 2R in the second schema, not 1/2R. Otherwise each node will draw twice the current, 4x more in total, than in the first schema. Now the important question: Are you asking about the heat of the wires, or the resistors? \$\endgroup\$
    – akwky
    Feb 21, 2022 at 8:36
  • \$\begingroup\$ Yes 2R. I’ll update it. I am asking about just the wire. \$\endgroup\$
    – BobaJFET
    Feb 21, 2022 at 16:44

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So, the heat generated in a wire is correlated to the current flowing through it (for a given wire). See, each wire has a set resistance per length, and so P=VI (P=I^2R) is the heat generated. Now, for the first case, lets say you generate P1 heat along that wire per length. For case 2, you will be generating P1 heat per length of wire since the same current is flowing through it. This holds true, until the node where half of the current branches off.

After branching off, those wires will each be carrying 1/2 the current, and so will be generating 1/4 the amount of heat per length of wire.

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