In order to do DC circuit analysis, you need to develop a sign convention when assigning polarities or current direction for each element in the circuit. Under the passive convention, the positive voltage reference mark is associated with the current reference arrow. Here, the device power is positive when it absorbs power and is negative when it delivers power. When both the current and voltage have the same algebraic sign, the device is absorbing power. Otherwise, if the current and voltage are opposite in sign, then the device is delivering power.

Below is a video to describe the passive convention used throughout this series of videos.

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