One kind of computer keyboard is based on the idea of

Chapter 19, Problem 19.128

(choose chapter or problem)

One kind of computer keyboard is based on the idea of capacitance. Each key is mounted on one end of a plunger, and the other end is attached to a movable metal plate (see Figure 19.19). The movable plate is separated from a fixed plate, the two plates forming a capacitor. When the key is pressed, the movable plate is pushed closer to the fixed plate, and the capacitance increases. Electronic circuitry enables the computer to detect the change in capacitance, thereby recognizing which key has been pressed. The separation of the plates is normally 5.00 103 m but decreases to 0.150 103 m when a key is pressed. The plate area is 9.50 105 m2 , and the capacitor is filled with a material whose dielectric constant is 3.50. Determine the change in capacitance that is detected by the computer. Ex