Determine the power dissipated in the 5.0 ohms resistor in the circuit shown in the drawing.

see the attachment for the diagram.

Attached Images

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For resistors in series R1 and R2, the equivalent resistance(R) ,
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For resistors in parallel R1 and R2, the equivalent resistance(R),
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First, group the resistors 2ohms and 1 ohms, 5ohms and 1ohms which are in series into single resistor first[LaTeX Error: Can't write to directory] [LaTeX Error: Can't write to directory]. Then Group the two requvalent resistors [LaTeX Error: Can't write to directory] and [LaTeX Error: Can't write to directory]which are in parallel into single resistor. Two resistors remain in series. Use the formula again.



Use V= IR to find the total current, then find the current through the 5ohms resistor. Power dissipated= (current)^2 X Resistance of resistor

In the problem neither the voltage of the source nor the current in any branch is given.
How to determine the power dissipation?

[quote=sa-ri-ga-ma;7093]In the problem neither the voltage of the source nor the current in any branch is given.
How to determine the power dissipation?[/quote

Sorry I forgot to put that in the diagram, the voltage is 12V.

The required power dissipation is = (5 x V^2) / 18 x 18where V is the voltage of the source.

Use V= IR to find the total current, then find the current through the 5ohms resistor. Power dissipated= (current)^2 X Resistance of resistor[/quote]

so...

1/Rz = (1/6)+(1/3)
Rz=2
2+4=6 final equivalent resistance(why do we add 4?)

I=V/R=12/6 =2

Then I'm lost after that.
How do I find the current through the resistor? is it just: I=V/R=12/5
and then what current and resistance do I use in the final equation?

The correct answer is supposed to be 2.2 W.

You add 4ohms because the total current(I) is to be found by grouping all resistors into 1 resistor.

Then [LaTeX Error: Can't write to directory] would be the voltage of the 4ohms resistor.
The voltage across [LaTeX Error: Can't write to directory] and [LaTeX Error: Can't write to directory]would be [LaTeX Error: Can't write to directory] as they are in parallel, so voltages are the same

So current[LaTeX Error: Can't write to directory]across [LaTeX Error: Can't write to directory] is [LaTeX Error: Can't write to directory]
Then the power dissipitated would be[LaTeX Error: Can't write to directory]X[LaTeX Error: Can't write to directory]