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I found an old question asked 5 years ago. How much power to keep surface of aluminum plate at given temperature?. How do I answer this in a physics kind of way?

This is my original answer:

By running a current through one kilogram of metal using a adjustable D/C power supply 1 volt to 12v and slowly increasing the voltage until you read enough resistance to achieve the temperature desired. You can also get an adjustable amperage as well but may cost more. Also try using an after market defroster for back windows of cars. Just stick it on the underside. The plastic insulator should keep the metal safe to touch and will be more efficient. Like a light it is the resistance to the flow of electricity that gives off the light and heat.

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Well... in this case, I don't know that it is possible to answer in a physics sort of way. I actually just voted to close it as an engineering question and thus off-topic for our site.

To answer the broader question of how to answer "engineering" questions with a physics way, I actually just attempted to do the same on a new post: Prevention of fluid vortex formation

As written, the question is sort of on the border -- it is clearly looking to solve a particular problem, but it is also asking for the concepts that are needed for the solution. The concepts are the physics, the design/numbers are the engineering. So to answer "engineering" questions in a "physics" way, it is usually sufficient to address the underlying processes that are needed to solve the problem. In the question I linked, it is explaining how/why the vortex forms and what the equation looks like so somebody could try to design whatever they needed based on the physics of the equation.

In your example, a "physics" answer would explain the mechanisms that lead to heating (the current flow for example) and the mechanisms that lead to cooling (radiation, convection, conduction, etc). Explain the relevant scales -- things like the non-dimensional numbers that describe the problem. Explain the assumptions made -- what does well insulated really mean? How does it change the equations or assumptions? Based on these things, perhaps provide some information on what terms are important or are insignificant in the governing equations.

Once all that is done, the OP should be able to solve whatever problem they wanted because you've explained the physics of the problem. The numbers, the techniques, the actual devices to get the solution are all off-topic. But the understanding of the mechanisms and equations, that's all physics and is spot on.

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