Solve Internal Resistance Homework Problem

AI Thread Summary
The problem involves a 6.0V battery connected to a parallel combination of a 10 ohm and a 40 ohm resistor, resulting in a total current of 0.25A. The combined resistance of the resistors is calculated to be 8 ohms. Using the equation E = IR + Ir, it is determined that the total resistance (R + r) must equal 24 ohms. While one calculation suggests the internal resistance is 16 ohms, the correct internal resistance is identified as 4 ohms according to the answer book. The discussion highlights the importance of correctly applying the formula to find the internal resistance.
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Homework Statement



"A 6.0V battery is connected across a parallel combination of two resistors ; one 10 ohm and one 40 ohm. Thee total current provided by the battery is 0.25A. Obtain a value for the internal resistance.


Homework Equations



E= IR +Ir

The Attempt at a Solution



I find the combined resistance of the resistors to be 8 ohms, and sub this into the equation above, and solve for little r, but get an answer of 16 ohms; the correct answer, according to the answer book is 4 ohms. Please can you show me a correct solution to the question!

Thanks
 
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Your answer is correct. Since 6.0 V produces 0.25 A of current, R+r must be 24 ohms.
10 and 40 ohms parallel is indeed 8 ohms, so r must be 16 ohms.
 

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