DC Circuits Homework: Calculating Power & Resistance

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Homework Help Overview

The discussion revolves around a problem involving a DC circuit with eight lights connected in parallel to a 119V source, including considerations of resistance and power calculations. Participants are exploring the implications of total resistance and power loss in the circuit.

Discussion Character

  • Exploratory, Conceptual clarification, Problem interpretation

Approaches and Questions Raised

  • Participants are attempting to calculate the resistance of each bulb and the power wasted in the leads. There are questions about the interpretation of total resistance and the setup of the circuit, particularly regarding the role of the leads' resistance.

Discussion Status

The discussion is ongoing, with participants providing various insights and suggestions for approaching the problem. Some guidance has been offered regarding the use of circuit laws and equivalent circuits, but there is no explicit consensus on the correct approach or calculations yet.

Contextual Notes

There are mentions of confusion regarding the definitions and applications of Kirchhoff's laws, which are not covered in the original poster's textbook. This may impact the understanding of the circuit analysis being discussed.

mustang1988
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1. Eight lights are connected in parallel to a 119V source by two leads of total resistance 2.5 ohms. If 240mA flows through each bulb what is the resistance of each? What fraction of the total power is wasted in the leads?


2. V=IR, P=I^2(R)



3. V=.24(119)=495.83/8=62ohms
P=(.24)^2(62)=3.57W
These are the answers i got but according to my book they are wrong. Can anyone tell me what I am doing wrong? thanks
 
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Well as for your first question you seem to have V=iV.

Now you know the resistors are connected in parallel.

To find the total resistance of all components, add the reciprocals of the resistances R of each component and take the reciprocal of the sum. :D.
 
Last edited:
2.5ohms is the total resistance? I thought that was just the resitence in the wire going from the battery and the wire going to the battery
 
Last edited:
In addition to what you already know about the circuit, you need (well, I suggest):

1) An equivalent circuit where you include a 2.5 ohms series resistor to represent the loss in the wires.
2) Kirchoff's Current Law
3) Kirchoff's Voltage Law
4) Ohm's Law
5) The expression for power.

Use them in that order, and see how that goes.
 
what is Kirchoff's current law and voltage law? they're not in my book
 

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