What are some factors that influence the voltage of voltaic/galvanic cells and why?

**Question:** (2014 USNCO local exam Q#41):



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> What types of changes would increase the voltage of a voltaic cell. 
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I have learned a bit about voltaic cells, but I haven't been able to find information about this anywhere.


What I know about voltaic cells is that to calculate voltage, you would need to know the standard reduction potential for the half reaction. Then, by adding the E(reduction) and E(oxidation) together, you would get the E(cell). The only way I can think of to change the voltage is by changing the reaction itself, or to change the standard conditions (temperature?). Electrons also flow from anode to cathode, so if more electrons are flowing across does that mean there's a greater voltage? I need help figuring this out.


