Since a Voltmeter does not account for the internal resistance of a voltaic cell, how can the actual EMF of the cell be measured?

Since a voltaic cell has some internal resistance the voltage measured by the voltmeter connecting the electrodes, is actually lower than the emf of the cell, so how can I measure the EMF of the cell exactly?




If you're stuck using a *low impedance* voltmeter, e.g. a D'Arsonval moving-coil meter, you could determine the cell resistance by drawing more current with a *known* resistance and noting the voltage drop.


From that, and the known resistance of your meter, you can then calculate the open-circuiit potential more accurately.


That said, high-impedance digital voltmeters are [available for less than US$7](https://www.harborfreight.com/7-function-digital-multimeter-63759.html), and the reading would be within the accuracy of the meter itself, *sans* calculation.


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