What the isn't this plug and chug?

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Homework Help Overview

The discussion revolves around the potential difference across a car battery being charged, specifically focusing on the effects of internal resistance and current. The subject area includes concepts related to electromotive force (emf) and battery behavior during charging.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants explore the formula for calculating the potential difference across the battery terminals, questioning the application of the equation used for discharging versus charging. There is a discussion about the implications of charging on the voltage and the sign of the internal resistance term.

Discussion Status

The discussion is active, with participants questioning the assumptions made regarding the charging process and the formula's applicability. Some guidance has been offered regarding the sign change in the equation, indicating a potential direction for resolving the confusion.

Contextual Notes

There is a noted lack of clarity in the textbook regarding the differences in calculations for charging versus discharging a battery, which has led to some confusion among participants.

mr_coffee
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A car battery with a 12 V emf and an internal resistance of 0.050 is being charged with a current of 60 A.

(a) What is the potential difference V across its terminals?

Okay i have an equation that should work perfectly!
Points a and b are located at he terminals of the battery, thus the potential difference Vb-Va is the termian to terminal potential difference V across the battery, we see that:
V = EMF - ir. r is the internal resitance of the battery, and they give me 60 amps as the current?
V = (12V)-(60A)(.050) = 9V, which is wrong!
 
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You are CHARGING the battery, not discharging the battery, so there is no way the resulting voltage would be lower than the nominal voltage...
 
I looked in the book and it gives me no case if ur charging the battery, what's the difference? It also didn't say that the formula i used is only for discharging a battery
 
A simple change in sign of the term "ir" maybe??
 
Ohhh! thanks again bigman! :biggrin:
 

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