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IP Computer Keyboards Many computer keyboards operate on
Chapter 20, Problem 95GP(choose chapter or problem)
Problem 95GP
IP Computer Keyboards Many computer keyboards operate on the principle of capacitance. As shown in Figure 20-16, each key forms a small parallel-plate capacitor whose separation is reduced when the key is depressed, (a) Does depressing a key increase or decrease its capacitance? Explain, (b) Suppose the plates for each key have an area of 47.5 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 0.425 pF, what is the minimum distance a key must be depressed to be detected?
Questions & Answers
QUESTION:
Problem 95GP
IP Computer Keyboards Many computer keyboards operate on the principle of capacitance. As shown in Figure 20-16, each key forms a small parallel-plate capacitor whose separation is reduced when the key is depressed, (a) Does depressing a key increase or decrease its capacitance? Explain, (b) Suppose the plates for each key have an area of 47.5 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 0.425 pF, what is the minimum distance a key must be depressed to be detected?
ANSWER:
Solution 95 GP:
Step 1 of 2:-
a)
Here, we have to find whether the spring key will increase or decrease the capacitance.
We know that,
.
As, “d” is in the denominator, by increasing this we are decreasing the capacitance of the capacitor.