Board logo

Adding resistor wattages?
tegwin - 6/12/07 at 04:43 PM

Im having one of those moments...

If I have two 1/4W resistors in parallel does that give me a 1/2W


And likewise, if I have six 3W resistors in parallel does that give me 18W?

I love speed :-P - 6/12/07 at 04:52 PM

http://en.wikipedia.org/wiki/Resistor#Series_and_parallel_circuits

JonBowden - 6/12/07 at 05:33 PM

simple answer is yes, if they have the same resistance

tks - 6/12/07 at 06:24 PM

this is a bit more difficult tough because
paralleling or series placing of resistos creates less or more resistance.

sow saying that you wattage rises isn't totally true, because the resistance is lower.

sow lets say you need 0,5watts and 100ohm.

Then you will need 4 x 1/4 watt of 100ohm resistors. and place them parallel and in series.

Tks

britishtrident - 6/12/07 at 07:17 PM

I squared R = watts

[Edited on 6/12/07 by britishtrident]

MikeRJ - 6/12/07 at 10:55 PM

quote:
Originally posted by tks
sow lets say you need 0,5watts and 100ohm.

Then you will need 4 x 1/4 watt of 100ohm resistors. and place them parallel and in series.


Or two 200 Ohm 1/4W resistors in parallel or two 50 Ohm 1/4W resistors in series.

Also note that a resistors maximum power dissipation is given for a particular ambient temperature (usualy 25C or 70C). Above these temperatures the resistors power rating has to be derated, and will reach zero Watts at some temperature.

[Edited on 6/12/07 by MikeRJ]