No current in homemade galvanic cell
Your small copper-zinc cell may not light up a bulb as often shown in textbooks. Check your ammeter settings, it must show some current. How are you connecting it in series? voltmeter is connected in parallel. Now an interesting question. Imagine you join 12 (e.g., Duracells) in series to generate about 12 Volts. Can one start a car with 12 Duracells? Why do you need a large car lead-acid battery? The answer lies in current. Same potential difference does not mean same amount of current supply. You may think 1 V is close to an ordinary cell, your single copper-zinc cell cannot supply enough current to even light up a bulb. Cell potential is a thermomdynamic concept. Current supply is a kinetic issue-how fast the electrons transfer to or from electrodes. Now you can think of the reason why there is no commercial battery made from zinc and copper. See Daniell cell for an interesting history. Check the size of electrodes in Daniell cells.