What prove that do you have that you have contracted a functional eletric cell

To prove that you have a functional electric cell, you would look for the following evidence:

• Voltage Measurement: A functional electric cell will produce a measurable potential difference (voltage) across its terminals when measured with a voltmeter. For example, a standard AA battery should show approximately $1.5\, \text{V}$.
• Current Production: When connected to an external circuit (a load, such as a light bulb or a resistor), a functional cell will drive an electric current through the circuit, causing the load to operate (e.g., the light bulb will glow).
• Chemical to Electrical Energy Conversion: The cell should be able to sustain this current flow for a period, indicating that it is converting chemical energy stored within it into electrical energy.