| MadSci Network: Engineering |
I don't believe so. Over the years that resistors have been manufactured, every conceivable value in the resistor code has probably been made. Whether they are available in your location and at the wattage you require is moot. I checked a few web sites and one belonging to Fairchild Semiconductor lists a few circuits they manufacture with "25 ohm output resistors," so they do exist. What is done when a resistor is unavailable is to combine other valued resistors in series/parallel circuits. For example to make a 25 ohm, you could use two 50 ohm resistors in parallel, or make a 3.2 ohm resistor with a three ohm and two 0.1 ohm resistors in series. Most electronic repair shops have a box of miscellaneous resistors, and when they need a value they don't have they will use them in series/parallel to substitute for it. And, common resistors, at least in America, are rated at plus or minus 20%. Therefore, given a supply of resistors that are rated at 3.0 ohms, there will be some that will measure 3.2 ohms when checked with an accurate meter.
Try the links in the MadSci Library for more information on Engineering.