If you try to measure the voltage of a battery with a voltmeter connected in series, as shown in the figure, you won't get a completely accurate measurement because of the internal resistance of the battery. To see how large this effect is, consider trying to measure the terminal voltage of a 3.200 V lithium cell having an internal resistance of 65 Ω by placing a 0.35 kΩ voltmeter across its terminals.
r = 65 Ω
R = 0.35 kΩ
A) What current, amperes, does the cell supply?

B) Find the terminal voltage, in volts.

C) To see how close the measured terminal voltage is to the emf, calculate their ratio.

 

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