I am helping a high school student with a physics experiment on internal resistance of a cell. My background is in chemistry, not physics.

Browsing SE for lab design, https://electronics.stackexchange.com/questions/524904/measurement-of-internal-resistance-of-a-battery pops up. Now the high school lab cannot generate square waves so I was looking for alternatives.

I understand that in an open circuit, emf is the same as the voltage across the cell. The school does not have a potentiometer. There are videos such as [this video at 4:20][1] that shows an open circuit, with an emf measurement. But wouldn't the cell form a circuit with the multimeter, thereby voiding the set up?

Please kindly point out what I am missing, and provide me with tips on how to avoid shorting the circuit and/or the multimeter. Thank you!


  [1]: https://www.youtube.com/watch?v=av38iBxcOgQ&t=260s