NTC thermistor heat dissapation calculation with graphs

In summary, the conversation discusses how to determine the maximum voltage that can be applied to a specific NTC thermistor without causing it to heat up above 65˚C. This is done by analyzing two graphs that show the resistance and heat dissipation of the thermistor at different temperatures. By finding the power dissipated and the resistance at 65˚C, the maximum voltage can be calculated using the formula V=√PR. Additionally, it is mentioned that a thermistor behaves like a resistor when it stabilizes.
  • #1
theanswerai
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1
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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  • #2
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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  • #3
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...
 
  • #4
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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  • #5
Thanks a lot for your help! 🙏
 
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1. How does an NTC thermistor work?

An NTC thermistor is a type of temperature sensor that works by changing its resistance in response to changes in temperature. The resistance decreases as the temperature increases, and vice versa. This change in resistance can be measured and used to determine the temperature.

2. What is the formula for calculating heat dissipation using an NTC thermistor?

The formula for calculating heat dissipation using an NTC thermistor is: P = (V^2)/R, where P is power dissipated in watts, V is the voltage across the thermistor, and R is the resistance of the thermistor at a given temperature.

3. How do I plot a graph for heat dissipation using an NTC thermistor?

To plot a graph for heat dissipation using an NTC thermistor, you will need to measure the resistance of the thermistor at different temperatures and then use the formula P = (V^2)/R to calculate the power dissipated. You can then plot the power dissipated on the y-axis and the temperature on the x-axis to create a graph.

4. What factors can affect the accuracy of heat dissipation calculations using an NTC thermistor?

There are several factors that can affect the accuracy of heat dissipation calculations using an NTC thermistor, including the accuracy of the temperature measurement, the stability of the power supply, the quality of the thermistor, and the thermal environment in which the thermistor is being used.

5. Can an NTC thermistor be used for both heating and cooling applications?

Yes, an NTC thermistor can be used for both heating and cooling applications. When used for heating, the thermistor will have a positive temperature coefficient (PTC), meaning that its resistance increases as the temperature increases. When used for cooling, the thermistor will have a negative temperature coefficient (NTC), meaning that its resistance decreases as the temperature increases.

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