Trying to understan this ampres thing

[demonds]

Well I got 3 question about this.

1. Is there a formula to find out how much ampres your system may be drawing?

2. If I have an amp the puts out 1000 watts rms does this mean that this is the wattage it will be suppliying the sub at all times or only when I turn my volume up? In other words, does higer volume means higer power output?

3. And last, I'll be putting a 1200 watts rms system in my car, my car has a 160 amp alternator with a 750 amp battery with a reserve capacity of 145, will this be enought to run my system? And assuming that the answer to my 2nd question is yes (higher volume meaning higher power output) I'm not planing to run my system at 1200 watts rms all the time, I just want to know that whenever I want I can, wich will make less power output if I run it at a moderate volume, thats assuming that the answer to my 2nd question is yes. Thanks for the help.

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[noob with an RS 10+ year member]

Well I got 3 question about this.1. Is there a formula to find out how much ampres your system may be drawing?

1. when i took an ASE-alternative electrical class i learned that the basic formula for watts is voltage x amps = watts. but there are some exceptions of which im not quite sure of so ask someone else for details i think it has something to do with being alternating current i dunno

2. yes.

3. And last, I'll be putting a 1200 watts rms system in my car, my car has a 160 amp alternator with a 750 amp battery with a reserve capacity of 145, will this be enought to run my system? And assuming that the answer to my 2nd question is yes (higher volume meaning higher power output) I'm not planing to run my system at 1200 watts rms all the time, I just want to know that whenever I want I can, wich will make less power output if I run it at a moderate volume, thats assuming that the answer to my 2nd question is yes. Thanks for the help.

3. you're electrical supply will do. you might want to do big 3 though. i have a 60-amp rated alt and a lower cranking amp battery and i havent even done the big three completely so you should be fine.

 

[ljb211087 10+ year member]

Assuming your amp is 70% efficient, i don't know if this is a reasonable figure, but anyways. The current drawn will be:

i=p/v

where i is unknown

p= 1560w (70% efficient)

v= 14.4v (If this is the quoted voltage for 1200wrms)

Therefore i= 108 amps

You have a little bit of reserve to play with @ 70% efficiency

 

[btnhfan 5,000+ posts]

Best way is to get a clamp meter.

 

[regal8r 5,000+ posts]

current draw- wattage/14.4v

wattage=voltage x current

voltage=current x resistance

 

[Bumpin' Yota 10+ year member]

everyone here is using P=IV and V=IR assumes that the phase angle of the current and voltage is the same in an alternating current setup. This is not the case...

when you crank it up to max output you will not be even close to 1000watts to the sub. The main reason is because the sub generated back EMF that fights the amp. This manifests itslef as a higher reactive impeadance. The secondary reason is above - the phase angles are different in an inductive load. Next if you have any kind of voltage drop and the amp is non regulated it will reduce overall power output.