Alternator comparisons

[fletcherson]

Each color is one particular gauge size. The lower right corner is 2 gauge
and it's good for 25 feet and 150 or 200 amps.

The round chart just give you all the different equations for calculating
Power, Resistance or Current. It's basically Ohm's Law.
P=Power
R=Resistance
I=Current

If you need to know the CURRENT so you can put in the proper fuse.
You also know VOLTAGE and RESISTANCE of the circuit, then you
can can find out the fuse size.
I=E/R (Remember I=CURRENT) .... I=13.5v/1.0 ohms = 13.5 amps ..... so use a 15 or 20 amp fuse.

Make any sense, feel free to ask another question.
.

Ohms law is one of the basic most useful calculations relating to practical electronics and electrical wiring. It's really pretty simple once you get it and mandatory to do it correctly. It takes the guess work out of it.