# Power generated by current and voltage sources

#### Isaac Tee

Joined Feb 21, 2018
5
Hi all,

I have seem to have come across a rather tricky question on the topic of power. I am familiar with calculating power across loads, but when it comes to independent sources, I am pretty lost. Attached are the question and the solution that came along with it.

I am supposed to calculate the power generated by the current sources and the voltage source. However, I do not understand what the solution is trying to tell me. I have tried superposition, but I realised I also came to another dead end when i couldn't treat the current sources as a load. Could someone help me on this? Thanks all!

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#### WBahn

Joined Mar 31, 2012
29,506
The solution is using the passive sign convention in the strict sense, which is that the power of any two-terminal component is the product of the voltage and the current entering the positive terminal. This means that the device is absorbing power if the power is positive and producing power if the power is negative.

Your solution for the power in the voltage source has the current coming OUT of the positive terminal, hence your answer will be off by a minus sign.

Also, you don't define either the I or the I4 so the reader (e.g., grader) has to guess. That is never a good thing. Annotate your diagram with every variably you use.

Also, learn to properly track your units.