Many computer keyboards operate on the principle of capacitance. As shown in the figure below, each key forms a small parallel-plate capacitor whose separation is reduced when the key is depressed.
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(a) Does depressing a key increase or decrease its capacitance?
increases or decreases ??
Explain
(b) Suppose the plates for each key have an area of 46.3 mm2 and an initial separation of 0.550 mm. In addition, let the dielectric have a dielectric constant of 3.75. If the circuitry of the computer can detect a change in capacitance of 0.403 pF, what is the minimum distance a key must be depressed to be detected?
______________________ mm