NTC thermistor heat dissapation calculation with graphs

AI Thread Summary
The discussion revolves around calculating the maximum voltage that can be applied to an NTC thermistor to prevent it from exceeding 65 °C. The user presents two graphs: one showing resistance as a function of temperature and another displaying heat dissipation at room temperature. By analyzing the graphs, it is determined that the power dissipation at 65 °C is approximately 320 mW, with a resistance of about 115 Ω. The calculation for maximum voltage yields approximately 6V, which is confirmed to be valid since a thermistor behaves like a resistor under stable conditions. The conversation emphasizes the importance of understanding thermistor behavior in thermal management applications.
theanswerai
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Homework Statement
The attached graph_1 represents the resistance R of a specific NTC thermistor as a function of its temperature ϑ. In the attached graph_2, the heat dissapation P of the thermistor at room temperature of 22 ˚C is displayed as a function of temperature of the thermistor.

Determine the maximum voltage that may be applied to the thermistor to prevent it from heating up above 65 ˚C!

Assume that the thermistor is initially at room temperature.
Relevant Equations
heat dissapation
I couldn't solve this problem. Any tips or help would be appreciated. If I am violating against any rules please comment, as this is my second post :-).
 

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theanswerai said:
Homework Statement:: The attached graph_1 represents the resistance R of a specific NTC thermistor as a function of its temperature ϑ. In the attached graph_2, the heat dissapation P of the thermistor at room temperature of 22 ˚C is displayed as a function of temperature of the thermistor.

Determine the maximum voltage that may be applied to the thermistor to prevent it from heating up above 65 ˚C!

Assume that the thermistor is initially at room temperature.
Relevant Equations:: heat dissapation

I couldn't solve this problem. Any tips or help would be appreciated. If I am violating against any rules please comment, as this is my second post :-).
Both graphs have Temperature on the horizontal axis. Draw vertical lines on the two graphs at 65C -- What two datapoints does that give you? How can you then use those two datapoints to determine the maximum applied voltage? :smile:
 
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The graph reveals that the power dissapated must be about 320 mW. The resistance at 65°C is about 115 Ω. Now we can simply plug in these values: $$V²=P*R⇒V=√PR⇒V=√36.8≈6V$$
Is this correct? I am not sure because this is how to calculate the voltage for a resistor and in this problem we have a thermistor...
 
Looks good to me. A thermistor is just a resistor with a high thermal coefficient of resistance. So when it stabilizes, it just looks like a resistor as long as the voltage across it is not changing.
 
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Thanks a lot for your help! 🙏
 
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