Author Topic: Resistor Wattage Rating  (Read 971 times)

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Offline mcintire265

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Resistor Wattage Rating
« on: June 05, 2016, 02:44:38 am »
First of all been watching the YouTube channel for a long time.  First post however here.

Found a bunch of resistors in a box I forgot I had and was wondering the easiest way to tell the rated Wattage.  They are smaller 4 band so it's not readily identifiable. 

Any suggestions greatly appreciated.

And yes by my post you can probably tell I'm an American haha.   Flood city area Pennsylvania.

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Online Brumby

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Re: Resistor Wattage Rating
« Reply #1 on: June 05, 2016, 03:32:35 am »
First suggestion is to take some photos - decent quality and reasonably close, please.  It would be good to have a ruler in the picture for scale.

Then we could offer some ideas.

Offline Simon

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Re: Resistor Wattage Rating
« Reply #2 on: June 05, 2016, 06:56:11 am »
The wattage loosely relates to the physical size of the component. Most resistor materials can only work up to a certain temperature and given the same sized component to dissipate more power you would need to increase the temperature. So in order to have the same maximum temperature for any given wattage you need to increase the size of the resistor. There are some exceptions where you get some older and poorer components that are larger for same wattage or on the flip side you get some modern resistors which are more expensive and more compact that can dissipate more power in the same package size. It's never a good idea to use any component at its maximum rating anyway and even a resistor datasheet can make for interesting reading. If you post the dimensions someone can cross-reference with some known stock and give you a rough idea.
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Offline Ammar

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Re: Resistor Wattage Rating
« Reply #3 on: June 06, 2016, 11:06:19 pm »
A typical through hole resistor will be rated at 1/4 W. If they are smaller than that they are probably rated at 1/8 W. However, as stated before pictures with some kind of scale would be useful as this is just a stab in the dark.

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