What causes current flow when dissimilar materials are coupled in a suitable electrolyte?

• A. Potential difference
• B. Temperature difference
• C. Color difference
• D. Physical contact alone

Answer: (A)

The driving factor is the potential difference between the dissimilar metals when they are in an electrolyte. That difference creates a galvanic cell: the more active metal becomes the anode and oxidizes, while the nobler metal becomes the cathode and reduces species in the solution. Electrons flow through the metal from the anode to the cathode, and ions move through the electrolyte to balance charges, forming a closed circuit. Without this electrochemical potential difference, mere contact or other factors like temperature or color won’t sustain current flow in the presence of an electrolyte.