# NTC thermistor heat dissapation calculation with graphs

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 :-).

#### Attachments

• Graph_1.PNG
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• Graph_2.PNG
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## Answers and Replies

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?

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: $$V²=P*R⇒V=√PR⇒V=√36.8≈6V$$