ooooooXXXXR2XXXXXR3XXXX(adsbygoogle = window.adsbygoogle || []).push({});

XXR1XXoooooooooooooooooXXXXX

XooooXoooooooooooooooooXooooX

XooooXXXXR4XXXXXXR5XXXXoooX

XoooooooooooooooooooooooooooX

XoooooooooooooooooooooooooooX

XoooooooooooooooooooooooooooX

XXXXXXXXX+BATTERY-XXXXXXXXX

X=WIRE

o= blank space (ignore)

R=resistor

battery= 9 V

Determine the power dissipated in the R4 resistor in the circuit shown in the drawing.

R1=3 ohms

R2=2 ohms

R3=1 ohms

R4=6 ohms

R5=1 ohms

So here is what i know so far. The resistance of R4+R5=7. The resistance of R2+R3=3. So the resistance of R2345=1/(1/7+1/3)=2.1 ohms. The total resistance through the entire circuit is R1+R2345=3+2.1=5.1 ohms.

So I use this total resistance to calculate the total current I=V/R so

I=9V/5.1ohms=1.76A. Now I can use this total current to calculate the voltage across R4 and R5. V=IR=1.76(2.1)=3.7 V across R4 and R5 since Voltage across parallel circuits are the same. I know power=IR^2=V^2/R.

But i cannot just plug in 3.7V^2/6ohms. This isnt giving me the right answer. I need to find the voltage across R4 only. I am not sure how to do this since the current is different passing through each resistor. please help and correct me if any of the previous steps i did were wrong. thanks.

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# Homework Help: Wired Circuits and Power

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