When you connect an unknown resistor across the terminals of a 1.50V AAA battery

Question

When you connect an unknown resistor across the terminals of a 1.50V AAA battery having negligible internal resistance, you measure a current of 18.3mA flowing through it.

If you now place the resistor across the terminals of a 12.9V car battery having no internal resistance, how much current will flow?

You now put the resistor across the terminals of an unknown battery of negligible internal resistance and measure a current of 0.459A flowing through it. What is the potential difference across the terminals of the battery?

Explanation / Answer

From ohms law we know that

                V =I*R then resistance is given by R =V/I =1.50V/18.3*10-3A=0.0819*103ohms =81.96ohms

Now If you place the resistor across the terminals of a 12.9V car battery having no internal resistance, how much current will flow is i =V/R =12.9V/81.96ohms =0.157A

now put the resistor across the terminals of an unknown battery of negligible internal resistance and measure a current of 0.459A flowing through it. What is the potential difference across the terminals of the battery is given by

                      V =i*R =(0.459A)(81.96ohms) =37.62V

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