# Find V_0 in the circuit (6 elements) (1 Viewer)

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#### VinnyCee

http://img68.imageshack.us/img68/51/problem120ha2.jpg [Broken]

Use conservation of energy to solve for $V_0$.

$$P_1\,=\,(30V)\,(-6A)\,=\,-180W$$
$$P_2\,=\,(12V)\,(6A)\,=\,72W$$
$$P_3\,=\,(V_0)\,(3A)\,=\,(3V_0)W$$
$$P_4\,=\,(28V)\,(2A)\,=\,56W$$
$$P_5\,=\,(28V)\,(1A)\,=\,28W$$
$$P_6\,=\,(10V)\,(-3A)\,=\,-30W$$

$$\sum\,p\,=\,p_1\,+\,p_2\,+\,p_3\,+\,p_4\,+\,p_5\,+\,p_6$$

$$\sum\,p\,=\,(-180W)\,+\,(72W)\,+\,[(3V_0)W]\,+\,(56W)\,+\,(28W)\,+\,(-30W)$$

$$3V_0\,=\,54W$$

$$V_0\,=\,18\,V$$

Does this look right?

Last edited by a moderator:

#### berkeman

Mentor
Looks okay until the last step (units).

EDIT -- BTW, this belongs in the homework forums, not the general forums.

#### VinnyCee

Do you mean the summation of the p's? I don't see a unit error, could you point it out please:)

I didn't see the "Engineering" Forum over at Homework help section, but now I found it, thanks for the heads up!

#### berkeman

Mentor
VinnyCee said:
Do you mean the summation of the p's? I don't see a unit error, could you point it out please:)
Vo should not have units of watts. Just a small typo.

#### VinnyCee

OIC, thank you!

$V_0$ should have units of Volts!

Other than that, the problem looks OK?

I will post other problems in the homework section, thanks for the help!

#### sauravlovesu2005

it is right if you are taking (3v) as a combination volt*amp. as previously u have takev 3*vo as power. so it looks right to me.

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