Chemical effect of electric current.
Explanation
The passage of electric current through a conducting liquid or moist medium causes chemical reactions to occur at the electrodes. This phenomenon is known as the chemical effect of electric current.
Analysis of the Phenomenon:
- Chemical Effect: A raw potato contains significant moisture and dissolved salts, allowing it to act as an electrolyte. When electric current is passed through it using copper wires, a chemical reaction takes place. A greenish-blue spot develops specifically around the wire connected to the positive terminal (anode). This color change is due to the formation of copper compounds resulting from the oxidation of the copper electrode and its reaction with the starch and ions in the potato.
- Comparison with other options:
- Heating effect: Refers to the generation of heat when current passes through a resistor (e.g., electric heater, bulb filament). It does not cause localized color changes in a potato.
- Magnetic effect: Refers to the generation of a magnetic field around a current-carrying conductor (e.g., deflection of a magnetic compass).
- Mechanical effect: Refers to the conversion of electrical energy into mechanical motion (e.g., electric motors).
Key Takeaway:
The formation of a greenish-blue spot around the positive electrode in a potato is a demonstration of the chemical effect of electric current and is often used to identify the polarity of a battery.