I want to simply control the speed of a 12v dc motor with the aid of some high wattage resistors. My voltage supply is 12v, the total current draw with resistors in series is 2.8amp. Now according to ohms law P = VI = 12 x 2.8 = 33.6watts. According to this R = V/I = 12/2.8 = 4.2ohm Total circuit resistance is 26.5ohm 24ohm + motor resistance. So if P also = V X V/R = 12 x 12/ 26.5 = 5.43watts if P = I x I x R = 2.8 x 2.8 x 26.5 = 207.76 I'm confused. I need to know what wattage resistor to use?