Calculate Current Through Battery Connected to Resistor

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To calculate the current through a battery connected to a 21-ohm resistor, the formula I = emf / (R + r) is used, where emf is the voltage of the battery and R is the resistance of the external resistor. The user initially attempted to calculate current using I = 12V / 21 ohm but encountered difficulties due to the lack of information about the internal resistance (r) of the battery. It was noted that the internal resistance must be included in the calculation for an accurate result. The user expressed frustration over not having sufficient information and sought clarification on whether there was an answer in the textbook for comparison. Ultimately, the discussion highlights the importance of knowing both the external and internal resistances to solve the problem correctly.
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Homework Statement



The voltmeter is removed (previous question was a voltmeter connected to a battery and it reads 12 V) and a resistor of 21 ohm is connected to the battery. What is the current (I) through the battery?


Homework Equations



emf=V
I=emf/(R+r)

The Attempt at a Solution



I tried to do I=12V/21 ohm but I don't know how to find R. When I entered the solution of that, it said to include the internal resistance of the battery, but I don't know the current of the battery so I can't use emf=IR to find R.
 
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Is there an answer in the back of the book to compare to?
 
haha nevermind. I was having trouble because I didn't have enough information, but I just didn't see where it was written. Thanks for your help anyway!
 

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