Then investigate each variable sseparately keeping everything else constant. Record your results. Determine how many cells and what type you need to connect together to light a tiny incandescent lamp. Jaycar or similar Procedure Cut Zinc and Copper Sheeting to suitably sized rectangular electrodes. Cut conduit pipe to small subsections to act as spacers between the electrodes to ensure the two plates do not touch one another.
Place electrodes into cups separated by the spacers and join the plates in series.
You can then break the circuit to connect the led or if you prefer you can already have it in place.