Compute Joule Heat in Heating Coils

In summary, two heating coils with resistances of 12.0 ohms and 6.0 ohms generate 9953W and 4976W of Joule heat, respectively, when connected in parallel to a 115V source. When connected in series, they generate 490W and 245W of Joule heat, respectively, with a current of 6.39A. The formulas used were P = V^2/R and I = Emf/R.
  • #1
BillJ3986
7
0

Homework Statement


Two heating coils have resistances 12.0 ohms and 6.0 ohms, respectively.
a)What is the Joule heat generated in each if they are connected in parallel to a source of emf of 115V?
b) What if they are connected in series.

Homework Equations


Am I doing this question properly?

The Attempt at a Solution


Since the resistors are in parallel. In order to find R effective I use the formula 1/12.0 +1/6.0=1/4 so my R effective is 4.0 ohms. I then needed to find the current, I. So I used I=Emf/R, I=115/4.0=28.8A, I think that is a little high.I use P=I^2(R), P=28.8^2(12)=9953W to find the joule heating in resistor 1? and then I did the same for the second resistor in parallel. P=28.8^2(6.0)=4976W.
For part B I had to find the current so I did I=Emf/r+r and they are in series so I just added them up to 18 ohms for my R effective. I found I, using I=115V/18ohms= 6.39A. P=6.39^2(12)=490W, second resistor p=6.39^2(6)=245W
 
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  • #2
Welcome to PF!

Hi BillJ3986! Welcome to PF! :wink:

Yes, that's all correct :smile:

but … why did you bother with finding the current in part a) ? :confused:

you know the voltage across each resistor, so just use the formula P = V2/R :wink:
 
  • #3
Thank you,

Yeah I'm looking over my notes now and I see that formula. I'm Glad I found this place, hopefully I can get my physics grade up a little higher. Thanks again for your input
 
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1. How is Joule heat calculated in heating coils?

Joule heat is calculated by multiplying the square of the electric current passing through the coil by the resistance of the coil and the time it takes for the current to pass through. This is known as the Joule-Lenz law.

2. What factors affect the amount of Joule heat produced in a heating coil?

The amount of Joule heat produced in a heating coil is affected by the electric current passing through the coil, the resistance of the coil, and the duration of time the current is passing through. Other factors such as the material and thickness of the coil can also impact the amount of Joule heat produced.

3. How can Joule heat be minimized in heating coils?

Joule heat can be minimized in heating coils by using materials with lower resistance, reducing the current passing through the coil, and decreasing the duration of time the current is passing through. Additionally, using thicker and more efficient coils can also help to reduce Joule heat production.

4. Why is it important to consider Joule heat in heating coil design?

Joule heat is important to consider in heating coil design because it can greatly impact the efficiency and effectiveness of the heating process. Excessive Joule heat production can lead to wasted energy and potential damage to the heating coil and surrounding components.

5. How does the type of heating coil affect Joule heat production?

The type of heating coil can affect Joule heat production as different materials and designs can have varying levels of resistance. For example, a copper coil will produce less Joule heat compared to a coil made of nichrome due to copper's lower resistance. The size and shape of the coil can also impact Joule heat production.

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