You are working on developing a way of testing the internal resistance of a batt

Question

You are working on developing a way of testing the internal resistance of a battery. The circuit you have created is shown above, with a battery (EMF and internal resistance r in the red box), a constant external resistor R1 = 17 ?, and a variable resistor R2. R2 has a resistance you can change over a wide range of values. You measure the voltage over R2, ?V2. The first resistor, R1, is there so you don't damage the battery by short-circuiting it.

In your measurements, you find that when R2 becomes very much larger than R1, the voltage ?V2 approaches a constant value, ?Vmax = 20 V.

You then measure that ?V2 = 0.45 ?Vmax when R2 = 21 ?.

What is the internal resistance of the battery? Give your answer in Ohms to three significant digits

Explanation / Answer

You are working on developing a way of testing the internal resistance of a batt

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