P1003: Unsung hero of the electrochemical cell – the wave front traveling near c
We present the electrochemical cell in a schematic that emphasizes distance traveled by an electromagnetic wave doing laps around the cell’s notional perimeter at near light speed. What could be the impetus for focusing on such an “exotic” aspect of the cell? A desire to close the gap between 20 minutes and 78 million years, where the former is the observed duration of a representative procedure (for the electrolysis of, say, 0.15g Cu), and the latter is the same procedure’s calculated duration based on the (generic) electrochemical cell presentation found in our textbooks. Per long-standing convention, where the student might reasonably expect a pedagogical model she is presented instead with a picture whose labels speak of a self-evident reality, wherein “electrons flow” from anode to cathode via a battery/lead system that serves as the “conduit” while ions migrate in solution “to complete the circuit.” If we take to heart that familiar picture, assigning rates 0.0002 m/s for electron drift and 0.000004 m/s for ion migration, the time required to react 0.15g of copper appears to be many millions of years; whereas, if we re-do the picture as a proper electric circuit, the calculated duration falls easily within the ballpark of the observed 20 minutes. The term ‘electron flow’ seems to speak of something tangible and edifying, but it should be accompanied by a warning label: Hard-Science Factoid. As it turns out, charges wafted by an ephemeral electromagnetic wave near c are what we need instead to make the numbers work.