power resstors and heat

[Groover]

ALL OTHER THINGS BEING EQUAL will a 10 watt resistor get less hot than a 5 watt resistor, or can it just tolerate more heat?

Please don't go off on a "it depends upon" dissertation. I said "all other things being equal" which means there is no change to any of the factors upon which it depends.

It seem like a simple question to me.

(Of course if the "it depends upon" factor has to do with the resistor itself, ie type of construction or the like, please feel free to point it out.)

[mooreamps]

ALL OTHER THINGS BEING EQUAL will a 10 watt resistor get less hot than a 5 watt resistor, or can it just tolerate more heat?

Yes to Both.

-g

[Steve Conner]

How many pancakes can fit in a doghouse?

None, because ice cream doesn't have bones.

Some resistors achieve higher wattage ratings in a small size by being made of stuff that can get extremely hot without damage. For instance, those green Welwyn ones are designed to run almost red hot at their rated dissipation, because they're made only of porcelain and nichrome wire.

Other resistors are made of stuff with less heat-resistant properties, so they make the higher wattage sizes physically bigger. The extra surface area lets them dissipate more heat without getting any hotter than the smaller sizes. For example, the Dale type aluminium housed ones, with their plastic potting, that need bolted to a heatsink.

Any free standing power resistor should have a datasheet that says what the surface temperature will be at rated dissipation.

[zhyla]

Any resistor of the same resistance will dissipate V^2/R amount of power. The actual surface temperature of the resistor will vary depending on the material and the surroundings. The wattage rating doesn't have anything to do with how much energy is coming out of the thing.