On Fri, 09 Oct 2009 21:40:42 -0700, Robert Baer
wrote:

John Fields wrote:
On Fri, 9 Oct 2009 02:15:50 -0700 (PDT), "larry moe 'n curly"
wrote:

When run at its rated power?

I'm referring to 1/4 - 10 watt resistors in TVs and PC power supplies,
probably in 30-50 Celcius surrounding air.

I thought that resistors were supposed to be chosen for twice the
actual power, but I've seen many 0.5W to 1.0W resistors run at almost
exactly their rated power continuously.

---
That's because it costs more to use a larger resistor than is necessary.

Let's say that you can get 1/2 watt resistors for a penny in quantities
of a million, and one watters for 1.5 cents.

If the 1/2 watters will do the job like they're supposed to and you buy
a million one watters instead, you've just thrown away $5000.00.

..only if you are stupid enough to not increase the sale price of the
widget by 50 cents per one watt resistor used.

---
Then your widget will cost more than an identical widget designed to be
lean, and your competition will eat your lunch.