Resolving Electric Circuit Questions: C & D

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Homework Help Overview

The discussion revolves around electric circuit questions, specifically focusing on questions c and d related to power calculations using the formula P=IV. Participants are exploring the implications of internal resistance in batteries and how it affects voltage readings.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • The original poster attempts to apply the power formula P=IV to solve the problems but questions the accuracy of their results, particularly for question c. Some participants inquire about the calculations leading to the results and the impact of internal resistance on voltage measurements.

Discussion Status

Participants are actively engaging with the problem, questioning the assumptions made regarding the battery's voltage and discussing the relevance of internal resistance. Guidance has been offered regarding the use of Kirchhoff's Voltage Law (KVL) and Ohm's law to analyze the circuit further.

Contextual Notes

There is mention of a paint document containing the questions, which may limit the visibility of the full problem context. Participants are also considering the effects of internal resistance on the voltage supplied by the battery.

Miike012
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Question is in paint doc... question c and d are what I am interested in...

For both questions I used P=IV, this gave me a correct answer for d but not c. For c I got 9/2 the answer is 4.3. Is that close enough? Or am I using the wrong equation?
 

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Miike012 said:
Question is in paint doc... question c and d are what I am interested in...

For both questions I used P=IV, this gave me a correct answer for d but not c. For c I got 9/2 the answer is 4.3. Is that close enough? Or am I using the wrong equation?

You should show more of your work. How did you arrive at 9/2 for (c)?
 
P =iv = 0.5a(9.0v)
 
Miike012 said:
P =iv = 0.5a(9.0v)

Ah. Well the power supplied by the battery is the power as delivered to external connections at its terminals. The batteries each include an internal resistance, so the voltage at the "9V" battery's terminals is not going to be 9V...
 
is there an equation to find the voltage at the 9V battery terminals?
 
Miike012 said:
is there an equation to find the voltage at the 9V battery terminals?

KVL, Ohm's law. What's the potential drop across the internal resistance?
 
Would it be 3?
 
Why did you guess 3?
 

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