Being I live in a small town is very hard to find the proper resistors.
Question. Can a 1/8 1/4 or 1/2 watt resistor be exchanged using the same Ohm ???
Reason Im asking is that I want a 150 ohm 1/4 watt, wondering if it would hurt to use a 1/8 or 1/2 watt as they are available localy.
Thanks in advance John
The resistor watt rating determines how much heat it can dissipate. The heat through a resistor (in watts) is given by I^2*R (the current in amps squared times the resistance). Exceed or come close to the resistor's rating and it will get very hot, and eventually destroy itself, typically becoming an open circuit.
For example, an LED circuit running at 12ma with a 1K resistor. .012 * .012 * 1000 = 0.144 watts. A quarter watt resistor or better will work; a 1/8 watt resistor will likely overheat and self-destruct over time.
Thus, you can substitute a higher wattage rating, but not a lower one than the circuit calls for.
Fred W
Depends on what yopu are using them for. You can go bigger, 1/2 watt in place of a 1/4 watt, with no problem. The actual power drawn will determine if you cna step down to 1/8 watt.
For example, if this is for 30ma incandescent bulbs, power in watts = current in amps squared times resistence in ohms. .030 x .030 x 150 - .135 wtt, more than 1/8 watt (.125) so you would burn up a 1/8 watt resistor.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Fwright an Rinker....Thanks for the excelent information, and a big thank you for helping others with your knowlege promoting the hobby. Both of you gentelmen always give great factual information, Thanks and have a great day
Only down side to using a higher wattage resistor is the physical size.