Hi guys,

I am currently taking circuit theory 1 and I have trouble in identifying power.

At first all I know is that I should use passive sign conv. and that if positive current enters a positive terminal then power is positive and it is absorbed and negative/supplied if negative current enters positive terminal or positive current enter negative terminal.

Now in this example I posted, it says that power for 30 ma is 5.4 w supplied, 9 ohm is 3.6 w, 6 ohms is 0.6 w, 12 ohm is 1.2 watt all absorbed.

couple of things i dont understand. How were they able to find the power? I know p equals vi, vi^2, or v^2/r. I also know how to find current by kcl and voltage by kvl but I donw understand how to assign the signs in the calcuation and when to know which element absorb or supplies power. Like do all resisters absorb and all current supply or does it depend on some factors. Guys I am lost. I have been thinking about this for the past 5 hours and my mind is going to explode. Can someone please help me. I am the type of guy who cant sleep until I understand something. please help.

Moderators note : retrieved image and uploaded it to the forum

I am currently taking circuit theory 1 and I have trouble in identifying power.

At first all I know is that I should use passive sign conv. and that if positive current enters a positive terminal then power is positive and it is absorbed and negative/supplied if negative current enters positive terminal or positive current enter negative terminal.

Now in this example I posted, it says that power for 30 ma is 5.4 w supplied, 9 ohm is 3.6 w, 6 ohms is 0.6 w, 12 ohm is 1.2 watt all absorbed.

couple of things i dont understand. How were they able to find the power? I know p equals vi, vi^2, or v^2/r. I also know how to find current by kcl and voltage by kvl but I donw understand how to assign the signs in the calcuation and when to know which element absorb or supplies power. Like do all resisters absorb and all current supply or does it depend on some factors. Guys I am lost. I have been thinking about this for the past 5 hours and my mind is going to explode. Can someone please help me. I am the type of guy who cant sleep until I understand something. please help.

Moderators note : retrieved image and uploaded it to the forum

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