Resistor Bud [for iOS]

Resistor Buddy is a full-featured tool for working with resistors. It has 4 modules that cover Ohm's law (R vs. I vs. V and power dissipation), Series circuit (Voltage drop, voltage divider, current, total resistance), Parallel circuit (voltage drop, current on each leg, total resistance), and color codes (find resistance from colors, or find colors to match resistance value).