When a capacitor is filled with an electrolyte (e.g. a salt solution), rather than an insulator, its behaviour is remarkably different: the capacitance is extremely high even when the distance between the plates is large, but builds up only slowly (in the order of seconds). Helmholtz first proposed the “electric double layer” (EDL) to explain this behaviour. Over the years, ever more sophisticated theoretical models of the EDL have been proposed. Practically, the EDL is used in the modern “supercapacitors”, which are a key technology e.g. for electric vehicles.
Here you shall study the build-up of an electric double layer experimentally, by applying a step-like voltage to an electrolyte-filled capacitor, and observe the charging transients on a digital oscilloscope. Investigate the dependency of charging transients on distance between the plates, and salt concentration.
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