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Emf of a batteryby pb23me
Tags: battery 
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#1
Mar3111, 10:25 PM

P: 207

1. The problem statement, all variables and given/known data
determine the terminal voltage in each battery. Emf_{1}=18V r_{1}=1 ohm EMF_{2}=12V r_{2}=2 ohm R=6.6 ohms also the batterys currents are opposing each other. 2. Relevant equations Vab=emfIr 3. The attempt at a solution i used kirchnoffs rule to find the current I , 18I6.612I2I=0 and got I= .625 then i thought i would just use Vab=emfIr to find the terminal voltage of each battery however im not getting the correct answer... could someone please explain this to me i have a test tomorrow morning and i really need to figure this out! the answers i got were 17.375 for the 18V batt and 10.75 for the 12V batt 


#2
Mar3111, 10:39 PM

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P: 11,678

Watch out for the current direction and the thus the polarity of the voltage drop it creates on the internal resistors. If current is being forced into a battery's positive terminal it's possible for it to have a higher terminal voltage than its internal EMF.



#3
Mar3111, 10:44 PM

P: 207

so on the larger voltage batt would i use equation Vab=EmfIr = 18(.625*1) and on the batt with voltage being forced across it use Vab=Emf+... idk



#4
Mar3111, 10:59 PM

P: 207

Emf of a battery
what are the equations you would use in this situation?



#5
Mar3111, 11:02 PM

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P: 11,678




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