eche, in our plant logs we always take heat *into* the system as positive q, and work *done by* the system as positive w. the common flip is mixing up the work sign—thinking work *on* the system is positive, like you're paying energy in.
i see it when new engineers calculate compressor duty, their w comes out negative and they panic, trying to add where they should subtract. houjik drama over a sign.
my life says the real mistake is staring at the textbook convention and forgetting which system you drew the boundary around—last week i spent an hour debugging because my 'system' was the reactor, not the cooling jacket.
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