Extra Credit

Rock and Roll Ain't Noise Pollution

This week's physics zen came courtesy of my car audio. When i was taking my friend home he thought it'd be fun to crank up the volume on my alpine deck to 18 (i listen to it at 7 usually) at 11:30 PM. After worrying that it would blow out my speakers because my amp is rated at 3000 watts, i remembered physics and, thanks to class, remembered how all that power was generated: capacitors.
Capacitors are like batteries in the sense that they are able to store energy. Unlike batteries however, capacitors are formed by two conducting plates that can hold equal but opposite amounts of charge, separated by a good insulator, which can be released instantly when the plates are put into contact. While they are not able to hold as much the fact that they can release all of their energy instantly and be recharged makes them very useful for car audio, which requires lots of power at volume 18 in my car. To charge a capacitor, a power source such as a battery moves the charge off one plate and adds it to the other until both have the same voltage difference. The ratio of charge on one of the plates to the overall voltage difference is called Capacitance, measured in Farads. Capacitance can be increased with the presence of a good dielectric, which reduces the field strength between the plates to allow more charge to be separated and thus discharged. After being discharged the voltage difference returns to 0 and can be charged again infinately.