Finding the power supplied by a battery

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Homework Help Overview

The discussion revolves around a multiple loop circuit analysis, specifically focusing on determining the power supplied by batteries within the circuit. Participants are exploring the application of Kirchhoff's rules and the relationship between current, voltage, and power in electrical circuits.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • The original poster attempts to use the equation p = I ε to find power, but expresses uncertainty about their calculations. Some participants question the appropriateness of the method used for calculating current and suggest that the actual current flowing through the battery should be considered instead.

Discussion Status

The discussion is active, with participants providing guidance on the correct approach to calculating power. There are multiple interpretations of the problem, particularly regarding the use of battery voltage and current calculations. Some participants are exploring the implications of using ideal versus real voltage sources.

Contextual Notes

There is a mention of potential confusion between the terms "battery" and "ideal DC voltage source," indicating a possible assumption that may need clarification. Additionally, the impact of load on battery voltage and capacity is noted, suggesting that external factors may influence the calculations.

snoweangel27
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I have a multiple loop circuit, which I was able to apply Kirchhoff's rules to in order to find the current of each resister. However, got stuck trying to determine the power supplied by the batteries (one in each loop). I tried using the equation p= I \epsilon, where \epsilon is the volts of the battery and I is volts of the battery divided by equivalent resistance of the loop that I am solving. Something seems to be wrong in my calculations, and I am not quite sure what I am doing wrong.
 
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snoweangel27 said:
I have a multiple loop circuit, which I was able to apply Kirchhoff's rules to in order to find the current of each resister. However, got stuck trying to determine the power supplied by the batteries (one in each loop). I tried using the equation p= I \epsilon, where \epsilon is the volts of the battery and I is volts of the battery divided by equivalent resistance of the loop that I am solving. Something seems to be wrong in my calculations, and I am not quite sure what I am doing wrong.

You probably did your nodal analysis wrong. If you calculated the currents correctly then you can use P=IV=I(IR)=I^2R .

Note that V is the power across the resister.
 
Note that battery voltage and total capacity will drop as the load increases.
 
Note that battery voltage and total capacity will drop as the load increases
I suspect that he's using the term "battery" where he really means ideal DC voltage source.

I is volts of the battery divided by equivalent resistance of the loop that I am solving

Well that sounds like the problem right there, why the heck would you do that? Why did you even bother calculating all the currents (presumably) correctly if you were then going to just ignore them and do something silly like what you stated above? The correct value of I to use here is the actual value of I flowing through the voltage source (or battery) in question. You can use Kirchovs current law to find the current in each voltage source from the other currents you have calculated.
 

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