The membrane around a cell normally has layers of charge that create a potential difference between its outer and inner surfaces. This difference is about 84 mV. When a singly ionized potassium ion moves channel in The membrane passing from The outside to The inside , what is The magnitude of The work done by The electric field of The membrane? Solution work done = charge * voltage = 1.6 * 10-19 * 84 * 10-3= 1.344 * 10-20.