Jif said:

hi

i am trying to wind or build a power resistor that is:

1.6 ohm and the resistor power is > 90 (12V*7.5(i))

what is the formula and what is a good wire to use i have may sizes of enamel copper

wire.

thanks

Jif

Well, there are several possibilities. You could use 1000 feet

of #12 copper wire which would be 1.619 ohms, but that's a

lot of wire. Maybe you could use a smaller gauge like #26

which is .0416 ohms per foot so you need about 38 feet.

At 90 watts you get about 2.3 watts per foot which wouldn't

heat up much assuming you spread out the wire so the air

can cool it off and keep the temperature down. The resistance

will increase a bit with temperature, but I don't have the

numbers.

Various copper wire sizes and resistances are:

Gauge / Turns per enamel inch / Resistance per 1000 ft.

10/9.6/1.018 12/12/1.619 14/15/2.575 16/19/4.1 18/23.6/5.5

20/29.4/10.35 22/37/16.46 24/46.3/26.2 26/58/41.6 28/72.7/66.2

30/90.5/105 32/113/167 34/143/266 36/175/423 38/224/673

-Bill