
#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

Mentor
P: 11,446

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

Mentor
P: 11,446




Register to reply 
Related Discussions  
Replacing a lead acid 12 volt battery with a Lithium ion Polymer battery  Electrical Engineering  15  
how to deal with battery in circuit  Electrical Engineering  2  
need help with replacing a leadacid sealed battery with a Lithium Ion battery  Electrical Engineering  5  
Battery  Introductory Physics Homework  2  
A batterybatteryresistor circuit  Introductory Physics Homework  2 