By using a capacitor the capacitor can supply power for the microcontroller in the split second that the voltage drops so that the microcontroller doesnt restart. This way it will filter out the noise on the power line. What Are Impedance Frequency Characteristics In Capacitors Capacitor Selection For Coupling And Decoupling Applications What Does The Voltage Rating On A Capacitor Mean This type of filtering is called decoupling. What does capacitors do . There are multiple capacitors within a given ac unit. Tune a radio into a station take a flash photo with a digital camera or flick the channels on your hdtv and youre making good use of capacitors. As the fuel covers more of a pair of plates the circuit capacitance increases. For instance there are start capacitors which send signals to start up the motor and run capacitors that regularly se...