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troubleshooting Question

# basic working of voltmeter

Math / Science
Hii

I asked a couple of questions a while ago about voltmeters but I have read over them again and I don't understand the answers so I will ask again and try and be clearer this time on what I am asking.

I am interested in the use of a voltmeter in a galvanic cell

Is it correct to say a voltmeter measures a potential difference across a cell? Which way round does the comparison go? Is the potential at the red lead compared to the black lead or vice versa. In other words, is it the potential at the red lead minus potential at black lead to vice versa

If the more negative potential is attached to the black lead and the less negative potential is attached to the red lead, will the potential difference be positive or negative?

What would be the potential be if you had the leads the opposite way.

I'm guessing it is the potential of the red lead minus the potential of the black lead. I have a diagram where it looks like the more negative potential attached to the black lead and the less negative potential attached to the red lead and the potential is positive. This would suggest it is red lead potential - black lead

Many thanks