Concepts about cell

[Primarygun]

I am trying to understand the chemistry cell thoroughly.

1.If there is only a copper wire connected to a multimeter, there should be no voltage, isn't it?

2. For the set up of a zinc electrode and a copper electrode, will I get a larger voltage by changing the electrode? Such as a more concentrated one, or potassium nitrate instead of magnesium(II) nitrate.

3.Concerning the set-up in no.3, why electrons can be given up by zinc atoms?

My idea: Zinc atom forms ions more readily in solution ( can it be pure water?) than contacted with copper wire.

4. Will there be any voltage if I use the zinc electrode instead copper electrode?

So far, I am learning chemical cells, please tell me some information. Thank you.