Quote:
Originally Posted by ANDYS87
Don't confuse household voltage(120/240V AC) with car voltage (12.5-14V DC). Its like comparing apples to oranges. With your car running, say you have 14V DC. Voltage can be related to the "pressure" pushing the current flow(like pressure pushing water out of a hose). 14 Volts of pressure isn't that much...car audio requires lots of current...add to that the fact that with DC voltage, the electrons have to flow from the battery...thru the load(stereo components, lights, etc)...then back to battery. There is a lot of resistance in the wiring. So, those are the reasons why you need humongo cables for high current draw accessories in your car(also why you need huge fuses). Now, in your house............120V AC....you have a lot more "pressure" to push the current(electrons)...also AC voltage is back and forth(sine wave)...Therefore, smaller wires and circuit breakers can be used.
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Actually if you are using the hose analogy,
the amperage would be the pressure and voltage would be the diameter of the hose, not the pressure.
The reason for the huge cables is that a low voltage (DC) signal requires a lot of amperage to do the same amount of work.
Ohms law: P=IV Power = Current x voltage
say you want 500 watts for your car stereo (DC.) You need 35.7 amps on that 14 volts to get the power you need. 14volts x 35.7Amps = 500 watts
now say you need the same 500 watts in your house (AC.) You only need 4.16 amps with the 120 volts. 120volts x 4.16Amps = 500 watts
Also capacitors for car audio are a waste of money. If you put a capacitor on an already taxed DC electrical system, you are not helping any. In DC analysis capacitors are treated as shorts anyway.