Potato Battery & Electrochemical Circuit Lab

1. Half-Cell Setup

Anode (-) Oxidation Metal

Cathode (+) Reduction Electrode

Potato Variety (Electrolyte pH & Ions)

Electrode Spacing: 3.5 cm

1 cm (lower R_int)8 cm

Insertion Depth: 3.0 cm

1 cm (shallow)5 cm (more surface)

“You stuck me with that zinc nail and copper penny and prayed to the heavens above that I would become an alarm clock...” — Sarah's sentient potato

Topology:

Target Load:

Connected Science Fair Apparatus

Digital LCD Alarm Clock

Requires ≥ 1.20 V & 15 µA

12:00

ACTIVE

Open-Circuit Voc

2.20 V

2 × 1.10 V per cell

Internal Res. Rint

480 Ω

Electrolyte ohmic drop

Terminal Vterm

2.19 V

Under active load

Loop Current I

36.5 µA

P = 80.0 µW

2. Electrochemistry & V-I Graph

Anode Oxidation (-)

Zn(s) → Zn²⁺ + 2e⁻

E° = -0.76 V (gives up electrons)

Cathode Reduction (+)

2H⁺ + 2e⁻ → H₂(g) (on Cu)

E° = +0.34 V (receives electrons)

Net Cell Potential ($E_{\text{cell}}$): 1.10 V

V-I Operating Curve & Load Line

Intersection (•) marks the closed-circuit operating point.

Electrochemical Note: Phosphoric acid in the raw potato provides hydronium ($H^+$) ions that are reduced to hydrogen gas at the copper penny, while zinc metal dissolves into the potato pulp.