This can be used to detect the ionization of air by radiation , see e.g. youtu.be/CZ7DoLLwW04?t=76 from Video "Ions produced by radiation carry a current by Institute of Physics".
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Electric potential, often referred to as voltage, is a measure of the potential energy per unit charge at a specific point in an electric field. It indicates how much work would be needed to move a positive test charge from a reference point (commonly taken as infinity or a grounded point) to the point in question, without any acceleration.