Why doesn't a resistor burn up when its power rating is exceeded?

Therefore, the power of the resistor was exceeded due to the water absorbing some of the energy, preventing it from burning up. In summary, the power of the 10ohm, 1W resistor was exceeded, but it did not burn up due to the cooling effect of the water.
  • #1
sarahjt1
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0

Homework Statement



The heating resistor is rated at 10ohms and 1W. By how much was its power exceeded? Why didn't the resistor burn up?

This is a question taken from an Electrical Equivalent of Heat lab assignment... here is a link to the exact same lab we did...

http://www.kbcc.cuny.edu/academicDepartments/PHYSCI/physics_12_14/pdf/Experiment4_EEquivalent_Heat.pdf

Homework Equations



P=V^2/R where V=10ohms and R=10ohms

The Attempt at a Solution



P=10W but the resistors rating was 1W and I don't really know why it didn't burn up. My only guess is that some of the power was lost due to the water absorbing some of the energy given off by the resistor?

Help! :confused:
 
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  • #2
sarahjt1 said:
P=10W but the resistors rating was 1W and I don't really know why it didn't burn up. My only guess is that some of the power was lost due to the water absorbing some of the energy given off by the resistor?

Your guess is correct. The ratings of power resistors do not take into account cooling them with water.
 

1. Why doesn't a resistor burn up if its power rating is exceeded?

Resistors are made of materials that have high resistivity and low temperature coefficients. This means that they are designed to have a high resistance to the flow of electricity and are able to handle high levels of power without overheating. Additionally, resistors are designed to dissipate excess power as heat, preventing them from burning up.

2. How do resistors dissipate excess power?

Resistors have a specific power rating that indicates the maximum amount of power they can safely handle. When this rating is exceeded, the resistor will heat up and dissipate the excess power as heat. This is why resistors often have a higher temperature when they are in use compared to when they are not being used.

3. Can a resistor ever burn up?

While it is possible for a resistor to burn up, it is very rare. As mentioned, resistors are designed to handle high levels of power and dissipate excess heat. However, if a resistor is exposed to significantly higher levels of power than its rating, it can overheat and potentially burn up. This is why it is important to choose the correct power rating for a resistor in a circuit.

4. What happens if a resistor's power rating is exceeded for a short period of time?

If a resistor's power rating is exceeded for a short period of time, it will heat up and dissipate the excess power. However, if the power rating is exceeded for too long, the resistor may overheat and potentially burn up. This is why it is important to monitor the power levels in a circuit and ensure they do not exceed the resistor's power rating.

5. How can I prevent a resistor from burning up?

The best way to prevent a resistor from burning up is to choose a resistor with a power rating that is appropriate for the circuit it will be used in. Additionally, monitoring the power levels in the circuit and ensuring they do not exceed the resistor's power rating can also help prevent overheating. Using heat sinks or cooling methods can also be effective in dissipating excess heat from resistors.

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