Resistors: What's the Watt information for?

[Rex]

Does the Watt listed (for the particular resistor in question) mean how
many Watt's it can handle before it breaks down and stops functioning
correctly? Or is it How much power it burns off in some unknown amount
of time? What does the Watt listed for a Resistor of some given value
mean?




Irrelevant side complaint (no need to read this part, I'm just venting):
I've looked in several beginning electronics books, the Library, online
resources & search engines, and haven't found the answer to the above
question. When doing a search online for a question like this its
difficult to filter out the bazillions of people who are trying to sell
Resistors. Good for the people who sell stuff, but whatever happened to
being able to get useful content out of a search? ...and why isn't a
Resistors Watt 'rating' (or whatever it is) explained in basic
electronics books? Do you have one that does? Know of a good free
content website that has the Resistor Watt explanation?

 

[John Larkin]

On Thu, 06 Nov 2003 01:13:51 -0000, Rex <user@example.net> wrote:

Does the Watt listed (for the particular resistor in question) mean how
many Watt's it can handle before it breaks down and stops functioning
correctly? Or is it How much power it burns off in some unknown amount
of time? What does the Watt listed for a Resistor of some given value
mean?




Irrelevant side complaint (no need to read this part, I'm just venting):
I've looked in several beginning electronics books, the Library, online
resources & search engines, and haven't found the answer to the above
question. When doing a search online for a question like this its
difficult to filter out the bazillions of people who are trying to sell
Resistors. Good for the people who sell stuff, but whatever happened to
being able to get useful content out of a search? ...and why isn't a
Resistors Watt 'rating' (or whatever it is) explained in basic
electronics books? Do you have one that does? Know of a good free
content website that has the Resistor Watt explanation?

If you google 'resistor power rating' the very first hit explains it
nicely:

http://www.tpub.com/neets/book1/chapter3/1-8.htm


John

 

[Lord Garth]

"Rex" <user@example.net> wrote in message
news:Xns942AAF735B1CAXn3w5p05t5@216.168.3.44...

Does the Watt listed (for the particular resistor in question) mean how
many Watt's it can handle before it breaks down and stops functioning
correctly? Or is it How much power it burns off in some unknown amount
of time? What does the Watt listed for a Resistor of some given value
mean?

It is the maximum rating the part can dissipate. You need a safety margin
so
stay at least 10% BELOW the power rating.

 

[Richard Mason]

On Thu, 6 Nov 2003, Rex wrote in
<<Xns942AAF735B1CAXn3w5p05t5@216.168.3.44>>

Does the Watt listed (for the particular resistor in question) mean how
many Watt's it can handle before it breaks down and stops functioning
correctly? Or is it How much power it burns off in some unknown amount
of time? What does the Watt listed for a Resistor of some given value
mean?

It's the maximum power the resistor can _continuously_ dissipate for a
given set of ambient conditions to achieve a possibly unspecified
reliability rating. A resistor doesn't just stop functioning if you
exceed the rated wattage but the killer is temperature and the higher
the resistors internal temperature the shorter its life - too high a
temperature and catastrophic failure occurs.

Take a look a the data sheets on a manufactures site e.g. www.vishay.com

--
Richard Mason

 

[Rheilly Phoull]

"Lord Garth" <LGarth@Tantalus.net> wrote in message
news:jmjqb.1715$ZK4.265@newssvr24.news.prodigy.com...

"Rex" <user@example.net> wrote in message
news:Xns942AAF735B1CAXn3w5p05t5@216.168.3.44...

Does the Watt listed (for the particular resistor in question) mean how
many Watt's it can handle before it breaks down and stops functioning
correctly? Or is it How much power it burns off in some unknown amount
of time? What does the Watt listed for a Resistor of some given value
mean?

It is the maximum rating the part can dissipate. You need a safety margin
so
stay at least 10% BELOW the power rating.


Probably learn about Watt's would be a good move too !!

--
Regards ............... Rheilly Phoull

 

[grahamk]

Rex wrote:

Does the Watt listed (for the particular resistor in question) mean
how many Watt's it can handle before it breaks down and stops
functioning correctly? Or is it How much power it burns off in some
unknown amount of time? What does the Watt listed for a Resistor of
some given value mean?




Irrelevant side complaint (no need to read this part, I'm just
venting): I've looked in several beginning electronics books, the
Library, online resources & search engines, and haven't found the
answer to the above question. When doing a search online for a
question like this its difficult to filter out the bazillions of
people who are trying to sell Resistors. Good for the people who
sell stuff, but whatever happened to being able to get useful content
out of a search? ...and why isn't a Resistors Watt 'rating' (or
whatever it is) explained in basic electronics books? Do you have
one that does? Know of a good free content website that has the
Resistor Watt explanation?

Hve a look at
Beginners and Intermediate Electronics
http://homepage.ntlworld.com/g.knott/index.htm