# How can I calculate the heat produced?

Discussion in 'General Electronics Chat' started by manorius, May 21, 2009.

1. ### manorius Thread Starter New Member

Apr 28, 2009
5
0
Hi guys,

I have a resistor cable and I want to heat it up to an x temperature
by applying y voltage. Is there an equation that I can calculate the temperature by using the length of the cable, resistance per cm and voltage applied?

Thank you very much!

2. ### Wendy Moderator

Mar 24, 2008
20,764
2,535
The real problem is the huge number of variables. If you insulate your resistor, or leave it open, or put a fan on it, will all affect the end answer. Even the shape of resistor will make a difference. Generally these kind of problems use temperature regulation feedback to control a temperature.

I once had a problem with a TEC (ThermoElectric Cooler) over heating on weekends. It was for a laser diode tester, and the heat dump was through a cutout in the table top. During the weekend the air became very still, and hot air rises, so eventually the air became so hot the heat dump (the heat sink under the table) couldn't get rid of the heat. The solution was to mount a fan underneath, and turn it on for 5 minutes every Monday. Normal movement around the table would keep it cool the rest of the week, since the stale air would be circulated.

IMO calculating the exact temperature is not practical, though you can measure it easily enough.

3. ### manorius Thread Starter New Member

Apr 28, 2009
5
0
Is there at least a way to find how many watts are being produced on the resistor?

Dec 19, 2007
2,574
230
P=(V x V)/R
P in watts
V in volts
R in ohms

Ken

5. ### Wendy Moderator

Mar 24, 2008
20,764
2,535
Even ½W, if it is properly insulated, can create high temperatures. Just as 10W, if it heatsinked and dissipated, will stay relatively cool. What are you trying to do?

6. ### russ_hensel Well-Known Member

Jan 11, 2009
818
47
The normal way to do this is to add a temperature sensor connected to a negative feedback circuit that controls the power to the reisistor as in thermostat.

7. ### thingmaker3 Retired Moderator

May 16, 2005
5,072
6
By "resistor cable" do you mean "resistance wire?" A heater element wire such as nichrome? If so, the charts on the following link might be of some help as a jumping-off point: http://www.heatersplus.com/nichrome.htm