Environment-resistor temperature

Hello to everybody, first of all sorry for my English (I'm Italian).

I have a circuit, enclosed in a plastic box, where there is power resistor 1K, 50W and Tmax=200 degrees centigrade. On the resistor is not present any heat sink.

After few hours that the circuit is working, the temperature measured on the case of the resistor (Tr) reaches 110 degrees, in a environmental temperature (Te) of 20 degrees.

My boss says that if Te increases50 degrees (Te = 20+50 =70 degrees), Tr will increase the same value (Tr = 110+50 = 160 degrees).

I would say that Tr will increase, but not so much, just a little bit. In my opinion it will be reduced the time for the resistor of reaching the maximum value.

Is my boss right? Am I right? Are we both wrong?

Thank to everybody is going to help me about this matter.


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"signo" a écrit dans le message news: snipped-for-privacy@g43g2000cwa.googlegroups.com...

Hello Massimo

Sorry ;o((

I think your boss is right

-- Guy Pastuzak


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guy pastuzak

For me it's important to know the true, it doesn't matter if my boss is right (he is always right...)

Thank you

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Your boss is (mostly) right.

If heat transfer were entirely by conduction, then the temperature difference would remain constant, like your boss says.

Although convection and radiation heat transfer are also occuring in the box, they are certainly minor compared to conduction.


Reply to
Tim Shoppa

Yesterday I've tried to test Tr with Te variable (from 20 degrees to 35 degrees). I can say that, with a tollerance of one degree, approximately the variation of Te is the same of the variation of Tr.

Thanks to everybody, Massimo

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