Many computer keyboards operate on the principle of capacitance. Each key forms a small parallel-plate capacitor whose separation is reduced when the key is depressed.
i) Does depressing a key increase or decrease its capacitance? Explain.
ii) Suppose the plates for each key have an area of 47.5 mm^2 and an initial separation of 0.550 mm. In addition, let the dielectric have a dielectric constant 3.75. If the circuitry of the computer can detect a change in capacitance of 0.425 pF, what is the minimum distance a key must be depressed to be detected?