Effect of lemon juice on voltage

[5arak1]

I did a science experiment for school. I added 100ml of water in beaker1 and 75ml of water and 25 ml of lemon juice in beaker2, 50ml of water and 50ml of lemon juice in beaker 3 and beaker 4 was 100ml of lemon. Here were the results:

Beaker 1: .542

Beaker 2: .504

Beaker 3: .543

Beaker 4: .567

 

When lemon juice was added(in beaker2) the voltage went down but when more lemon juice was added it went a bit higher, can someone explain why this happened in scientifically? I searched alot over the internet and could only find this:

 

The lemon juice contains a big amount of acidic juice, which in scientific terminology is an electrolyte. The acid in the electrolyte breaks down the atomic structure of of the copper and zinc, causing individual electrons to be released. The copper strip and the aluminum strip are the electrodes. They allow electrons to move freely through them.

 

Can someone please explain why this actually happened..?

Thank you, sorry if this is in the wrong section or something...

[gonelli]

If you have electrochemical cells and the concentrations of your reductant and oxidant are not standard (i.e. not 1M) then the Nernst equation should be what you want to look at.

http://en.wikipedia.org/wiki/Nernst_equation