Watts=Amps?

Correction, how many amps a device draws based on the wattage it puts out?

Hey Day952.....Power (watts) = I (current) X E (voltage) or

I (current) = (P Watts) divided by E (voltage)

example   I (current) = 100W / 12V or 8.333 amps

Hope this helps......

can you explain why the fuses in cars are so high? like for a small thing like a fuel pump which i'm sure does not run at 100watts... (the wire is really thin and it's like probably 5-10 watts most), the fuse for this is like 15amp?

Correction, how many amps a device draws based on the wattage it puts out?

Keep in mind that while P=I*V, the wattage something PUTS OUT may be less than the wattage (and therefore current) it DRAWS IN.  What is missing from the equation in that case is EFFICIENCY...

Simply using P=IV to determine current draw from wattage OUTPUT assumes 100% efficiency which is not possible in such a case as an amplifier.  Most class A/B amps are between 50-60% efficient, while a Class D will be about 70%+ efficient at most power levels.  (At full power output Class D amps drop in efficiency to around 60% or so much like an A/B amp, just a little better in most cases).

For example, if your amp puts out 120W and is only 50% efficient it means its power supply draws 240W to output that power.  In this case, at 12V, the current DRAW would be 20A, not 10A as one would mistakedly calculate without considering efficiency.