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# Feedback Comments on Thermal Energy

by Ron Kurtus

A total of 374 comments and questions have been sent in. They are listed according to date.

You can read them to further your understanding of the subject.

## List of next 10 letters

### Country

Thermodynamics Heating a waterbed warmer than your body temp USA

Heat How does heat move along an iron rod? India

Thermal Insulation I don't understand insulation Ethiopia

Temperature Limits How can the speed of light not be the maximun? USA

Temperature Defining temperature in a solid with no motion of atoms Pakistan

Heating a Greenhouse Wants water based radiant in floor heating Canada

Temperature Measurement Is each degree in a thermometer the same? India

Temperature Measurement How can I measure temperature without a thermometer? Rwanda

Thermodynamics Zeroth Law of thermodynamics India

Thermos Is it possible to build a 50 gallon thermos? USA

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First 10 letters

## Heating a waterbed warmer than your body temp

Topic: Thermodynamics

### Question

July 17, 2009

My waterbed should be slightly higher than body temperature?

My body creates heat - constantly. BUT it insists on keeping its temperature constant. It seems to me that it is very unhappy, if it does not loose the heat it produces. It loses the heat it produces to the environment: the waterbed and the air surrounding my body.

If the air is particularly cold, a warm(er than body temperature) waterbed would be nice. But if the air is "warm", then a slighter cooler (than body temperature) waterbed would seem more comfortable.

John - USA

18033

### Answer

When you are lying on your waterbed, there is a tendency for both to reach an average temperature. Since the mass of the waterbed is much greater than your body, it acts as a "heat sink" in that is seems to suck heat from your body.

Ideally, the waterbed should be at your body temperature. But since it loses some heat to the air, having it slightly warmer would keep it comfortable. On a hot day, a slightly cooler waterbed might be more comfortable. That is why they usually have heaters with an adjustable thermostat. Then you can adjust the temperature to what is comfortable.

The big issue, though, is that many people don't realize that the water must be heated. Water at room temperature would be uncomfortable in a waterbed.

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## How does heat move along an iron rod?

Topic: Heat

### Question

June 13, 2009

HOW HEAT MOVES FROM ONE POINT OF AN IRON ROD TO ANOTHER

GOKULESAN - India

17902

### Answer

When you heat an iron rod, you are giving its molecules energy and causing them to move faster. The high energy or faster molecules bump into nearby low energy iron molecules, causing them to move faster. In this way, the heat moves along the iron rod from the hot or high energy end to the cool or low energy end.

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## I don't understand insulation

Topic: Thermal Insulation

### Question

May 20, 2009

i don't anderstand the ideas about insulation system

hamza - Ethiopia

17778

### Answer

Thermal insulation is preventing the flow of heat through a material. Metal conducts heat from one end to another quickly. But good insulators don't/

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## How can the speed of light not be the maximun?

Topic: Temperature Limits

### Question

May 15, 2009

In the section on the speed of light. You state that is a misnomer because light itself cannot reach that speed. If we call " the speed of light " c how was this theoretical speed determined if not by measuring the actual speed of light? Was it Lorentz or Einstein who first expressed the c factor?

Aldo - USA

17751

### Answer

Just as Absolute Zero is an entity that never can be reached, so too is "c" a limitation property of space. Light particles or photons have zero rest mass, but they exhibit properties of mass such as momentum when traveling at the speed of light. We aren't sure if there are other particles, such as gravitons, that may travel at a slightly greater speed than the speed of light.

Whatever the case, the difference between the speed of light and "c" is so small that we can consider them equal. My comments on them may be simply nitpicking.

Einstein formulated the mathematics for his theory of special relativity, which proposed that the speed of light was a limitation, while Lorentz explained various phenomena that occurred when objects approach to the speed of light. This was named the Lorentz transformation.

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## Defining temperature in a solid with no motion of atoms

Topic: Temperature

### Question

April 28, 2009

how can we define teperature in case of solid where there is no translational motion of atom or molecules at all ?

javed - Pakistan

17668

### Answer

Even though the atoms or molecules in a solid are kept in place by a crystal matrix, such that there is no translational motion, the atoms still vibrate in place. This gives them their kinetic energy. The only time there is no emotion at all is at Absolute Zero.

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## Wants water based radiant in floor heating

Topic: Heating a Greenhouse

### Question

April 14, 2009

Thank you for providing this site / information.

I am in my 60's and in the process of learning/figuring out how best to install water based radiant in floor heating. I took one university level course in physics and vaguely remember some content. I have been researching about the absorption of radiant/infrared heat into concrete and into the human body.

I am sure there must be better science to the design / installation of radiant heat than what I have found!

My current plan is to construct the main floor in the traditional plywood finish, put down the pex water pipe and then pour 1 1/2 inches of real concrete over it. Then ceramic tile over that. The concrete will Radiate heat and based on one Emissivity value I found will radiate energy in the area of 2 to 5.6 nm wavelength.

I then tried to find out what are the best wavelenghts for the human body to absorb radiant energy and I guessed that the absorbtion characteristics of water would be my best bet in an attempt to fine tune the radiation heat.

Can you point me to a couple of sources and/or answer some of these questions:

1. what wavelength should we try to design to emit from the concrete/tile [it looks like the texture of the finish might be able to impact the infrared wavelength] in order for people to best absorb/feel the heat. The range seems to be 2nm to 5.6 nm. Any filler one could/should add to the concrete to improve / fine tune the radiant wavelength?

2. same as 1, what wavelength radiated from the concrete-tile would be best to reflect heat back into the house from windows in the house?

3. Should I spray the plywood floor with an aluminum paint that has very high reflection property so that most of the radiant energy from the hot water will reflect away from the plywood floor into the concrete mass - room

4. does the energy radiate from the concrete to the tile or is that done via conduction? According to one table I have found, rough concrete finish produces higher emissivity than smooth concrete - does this make sense from a physics perspective?

5. Is there a particular colour / texture of tile that will help optimize the range of radiant waves that are "just the right' wavelength for absorption by human skin/body?

Any help would be appreciated .. Thanks you

claus - Canada

17601

### Answer

Don't try to "reinvent the wheel" by going into such detail to install water based radiant in floor heating. There are many companies that have information and hardware for installing such a system.

http://www.radiantec.com apparently sell kits for installing.
http://www.radiantdirect.com provides hydronic radiant floor heating systems.
http://www.radiantdesigninstitute.com/ provides information, including costs.

I am sure you can find dealers in your area that can help in getting radiant heat for your house. It is better to deal with experts than to try to start from scratch yourself.

Best wishes in setting up your heating system.

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## Is each degree in a thermometer the same?

Topic: Temperature Measurement

### Question

April 9, 2009

How do we know that each degree in a thermometer represents equal amount of heat

sushil - India

17580

### Answer

The temperature of the object is a measurement of its average thermal energy. Heat is defined as the transfer of thermal energy.

A Celsius degree is 1/100th of the difference between freezing and boiling points of water. The assumption is that the change in thermal energy is the same for each degree.

But that may not be true, because the material in a thermometer that is based on expansion may not expand linearly with temperature.

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## How can I measure temperature without a thermometer?

Topic: Temperature Measurement

### Question

March 30, 2009

plz, give me five manners used to measure temperature without using thermometer

AIME - Rwanda

17529

### Answer

A thermometer is the only device to measure temperature. There are different types of thermometers. Some use colored liquid, some use bending metal and some use changes in electricity. You cannot measure temperature without a thermometer. But you can detect heat without one.

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## Zeroth Law of thermodynamics

Topic: Thermodynamics

### Question

March 28, 2009

WHAT IS ZEROTH LAW OF THERMODYNAMICS?

BIJULAL - India

17519

### Answer

A system is said to be in thermal equilibrium when its temperature does not change over time. It results from the definition and properties of temperature.

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## Is it possible to build a 50 gallon thermos?

Topic: Thermos

### Question

March 24, 2009

I am in the 10th grade and have been thinking of something for some time now. Would it be possible to build a 50 gallon Thermos bottle? If a Thermos bottle can keep water hot for many hours, wouldn't the same science work to keep water hot in home water heaters? I thought of using a heavy duty plastic tank with an interior reflective flask, and vacuum sealed. Conclusion? fuel sourse would not come on as often, thus saving the homeowner lots of money each year. I would like to know what others think about this idea? Thank you from Virginia, USA

Joe - USA

17502

### Answer

Your idea is good, but to a degree it has already been done.

The hot water heater in most homes can be thought of as a large thermos bottle. Typically, the container for the water is wrapped in a layer of insulating material and then held in place with the outer steel shell. Some inexpensive water heaters have a thin layer of insulation. If the out shell feels warm to the touch, people can buy a fiberglass insulation blanket to wrap around it.

With a small thermos bottle, the area between the inner container and outer container is often a vacuum. But evacuating a large container is too expensive to be practical. That is why they use insulating material.

Keep think of the ideas. That is how progress is made.

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