Lemon Cell Series with LED Illumination

The simulation models a string of lemon electrochemical cells, each formed by a zinc nail and a copper electrode. The emf of a single cell depends on the metal pair (≈0.90 V for Zn|Cu, 0.60 V for Fe|Cu) and each cell has an internal resistance that grows with electrode spacing. When cells are joined in series their voltages add while internal resistances also add, forming a simple series circuit that can drive an LED.

Students can change the metal used for the electrodes and increase or decrease the number of lemons. The app displays the total emf, the combined internal resistance, and the terminal voltage that appears across the LED. By watching the LED turn on or stay off, learners see how series addition of cell voltages and internal resistance affect the current that flows through a non‑linear load.

Through this activity students learn the basics of current electricity, series circuits, and the relationship between emf, internal resistance, and load characteristics such as the LED’s I‑V curve. They also see how electrochemical cell chemistry influences electrical output.