[Boatanchors] carbon resistor wattage ratings

[Jim Brannigan]

Heat is heat, is heat, is heat..........
The wattage of a resistor is the ability to deal (dissipate) with the heat, 
not how cool it will run.

A Google search or a drill down in one of the electronics catalogs should 
bring you to the manufacturers specs.

Jim

> Can somebody set me straight on what is acceptable as regards surface 
> temperature related to wattage rating of carbon resistors?
>
> After I calculate the proper rating using the standard power formulae, I 
> then choose the next higher standard wattage rating and after placing the 
> resistor in circuit I use a temperature probe to check it. In a recent 
> example, I found P=.196W so I needed a 1/4W resistor but I only had a 1/2W 
> and the temp probe gave me a reading on that resistor of 50deg C (122deg 
> F). To the touch, that feels too hot. I cannot keep my finger on it for 
> very long. I recalculated the I_ squared_ R and again it came up with 
> .196W so 1/2W should be fine.
>
> Please enlighten me.
> Thanks and 73, Dick KF4NS
> St Petersburg, FL 33714 USA
> Keep The Glow!
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