Power Resistor Immersed In Water

In summary, the circuit shown has a 20-ohm resistor immersed in water surrounded by insulating foam. The equivalent resistance through the circuit is 40 ohms and the current through it is 0.75A. Using the equation P=I^2*R, the power dissipated through the 20 ohm resistor is calculated to be 11.25W. However, the given solution of 22.5W appears to be incorrect and may be the power dissipated in the entire circuit. The presence of water and insulating foam will not affect the power dissipated, but they may impact the temperature.
  • #1
elements
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Homework Statement


For the circuit shown below the 20-ohm resistor is immersed in water surrounded by insulating foam; the equivalent resistance through the circuit is 40 ohms. The current through it is 0.75A. What is the power dissipated through the 20 ohm resistor?

Homework Equations



$$ P=I^2*R$$

The Attempt at a Solution


$$ P=0.75^2*20$$
$$ P=11.25W$$

The solution to this problem gives 22.5W, why is the power dissipated through the resistor doubled here? Does the water or insulating foam affect the power at all? or is power calculated for the entire circuit?
 
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  • #2
The water and insulating foam do not affect the power dissipated, but they will certainly affect the temperature. The higher the insulation, the higher the steady-state temperature will be. Are there 2 resistors in the circuit? If 0.75 A is running through 40 ohms, then you can calculate the power from the equation you showed above. However, it should be P = I2 * R
 
  • #3
Sorry forgot to give the picture
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  • #4
elements said:
The solution to this problem gives 22.5W

It looks like the answer they gave is wrong.
 
  • #5
That would be the power dissipated in the whole circuit (all the resistors). Perhaps check the wording of the question?
 

1. What is a power resistor immersed in water?

A power resistor immersed in water is a type of resistor that is designed to be submerged in water while still maintaining its functionality. It is typically used in applications where heat dissipation is required, such as in water-cooled electronic systems.

2. How does a power resistor immersed in water work?

The resistor is made up of a resistive element, usually made of a metal alloy, that is encased in a waterproof material. When an electrical current passes through the resistor, it generates heat which is then transferred to the surrounding water, allowing for efficient heat dissipation.

3. What are the benefits of using a power resistor immersed in water?

One of the main benefits of using a power resistor immersed in water is its ability to dissipate heat more efficiently compared to other types of resistors. This can help prevent overheating and damage to electronic components. Additionally, the water can act as a natural insulator, providing extra protection against electrical shocks.

4. What are the potential drawbacks of using a power resistor immersed in water?

One potential drawback is the risk of water damage if the resistor is not properly sealed or if the water is contaminated. The use of water also adds complexity to the design and installation process, as it requires additional components such as a water pump and plumbing.

5. What are some common applications of power resistors immersed in water?

Power resistors immersed in water are commonly used in high-power electronic systems, such as in industrial machinery, power generators, and high-performance computers. They are also used in applications where space is limited, as the heat dissipation can be more compact compared to other cooling methods.

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