Simple, everyday science

[betazed]

Hmmm, I dont mean to be a spoil sport, but I dont think mine is incorrect. To heat a large space to a certain temperature requires more energy than it takes to heat a smaller space to the same temperature.

true, but I think the question was once all else being equal if you have heated two bodies to different temperature would it take the same amount of energy to keep them at their respective temperatures?

The answer is no owing to rate of heat transfer being dependent on temperature difference.

 

[El_Machinae]

I agree, but I think you're only including initial heating cost (which I accept is 3 hours of furnace) ... since my house doesn't change in size (often, except when I have one of my mondo sneezes), what does size have to do with my thermostat?

 

[Bozo Erectus]

Youve got X volume of air. To heat it to temperature X, requires X amount of energy. If you want to raise the temperature of that same volume of air further to Y, it requires Y (more) amount of energy. If the volume of air is small enough, it'll require only X energy to heat it to Y.

Why?

I dont know!

Third base!

 

[nonconformist]

Yeah, I thought my answer would be correct.
Heat effectively "flows", so a bigger difference would create a bigger "flow"

EDIT: Or a "potential difference" even.

 

[mrtn]

Bingo! The liquid water laps up and down, depositing water around the edges of the hole, which then freezes. More water splashes over the new higher edge, freezes, and so on.

At least thats the conclusion that I came to.
...

I've seen this fenomenon after ice drilling too, but I don't really buy your explanation.
Why would you have waves on a little patch of water 10 cm (or 1 dm as we ISO-certified Europeans say) across?

 

[Renata]

I still want to see a picture ...

I get what it's supposed to look like, now, but I don't think I've ever noticed it.

 

[Sims2789]

Ice leaks out and a tiny bit freezes very fast, causing water to freeze atop this ice.There is a sheet of new ice where the water leaked. The ridge is due to ice building up.

 

[El_Machinae]

If I park my car outside overnight, and I don't want frost on it in the morning, am I better off parking it with a 'warm' windshield or a 'cold' windshield?

 

[Birdjaguar]

If I park my car outside overnight, and I don't want frost on it in the morning, am I better off parking it with a 'warm' windshield or a 'cold' windshield?

In New Mexico where there is very little moisture in the air, it probably doesn't matter. Elsewhere, a cold windshield would produce less condensation and hence less ice. ??? Something I wrote sounds off, but I'm not sure what. Hmmm.

 

[Mylon]

Running your Air Conditioner (for heating or cooling) at a lower setting will save energy because heat transfers at a rate proportional to the temperature difference. That is, an 100C object in a 0C environment will loose temperature (and energy) faster than a 80C object would. Thus, maintaining the object at 100C costs more energy than maintaining it at 80C. Insulation will reduce the amount of energy in both cases, but it will still take more for the 100C case.

As for the rings of ice... When the ice initially forms, it starts at the water level. As it thickens, the water level rises because the ice expands and it can't expand downwards. When a break in the ice is formed, the ice level is above the water level and the water stays where it is, eventually freezing in place. This creates a depressed crater where the ice was broken.

 

[Perfection]

correct. IIRC, it is directly proportional to the fourth power of the difference in temperatures.

You're thinking about Blackbody radiation (which is directly proportional to the fourth power for total temperature. The rate of heat tranfer via conduction is directly proportional to the difference in temperature.

 

[El_Machinae]

C'mon ... my car windshield question needs answering soon ...

 

[Birdjaguar]

C'mon ... my car windshield question needs answering soon ...

You didn't like my answer in post 29? Leave it cold.

 

[Perfection]

If I park my car outside overnight, and I don't want frost on it in the morning, am I better off parking it with a 'warm' windshield or a 'cold' windshield?

You'll get less frost on the inside of the windshield if you leave your entire car cold (there'd be less water inside to condense).

On the outside you can't do squat about it. By the time frost forms your windshield will be cold.

 

[ainwood]

The rate of heat tranfer via conduction is directly proportional to the difference in temperature.

For a house losing heat the the surroundings, convection would be determining medium.

 

[Perfection]

For a house losing heat the the surroundings, convection would be determining medium.

While convection is the medium for the exterior of the house losing heat to the environment, conduction is the medium for the interior to the exterior. That's why we have insulation.

 

[ainwood]

And how does the energy get from the air to the walls?

 

[Pontiuth Pilate]

When the ice initially forms, it starts at the water level. As it thickens, the water level rises because the ice expands and it can't expand downwards. When a break in the ice is formed, the ice level is above the water level and the water stays where it is, eventually freezing in place. This creates a depressed crater where the ice was broken.

This is the correct explanation. You can observe the opposite effect by putting some ice cubes in a glass of water, then putting the glass in the freezer. Some lumps (the ice cubes) will stick above the flat surface of the ice, because as the water freezes, the already frozen cubes rise and float above it.

 

[Pontiuth Pilate]

OK, next question (pretty easy one):

Using a straw, you can drink a glass of water. However, if you were to go to the third floor of a building and try to drink a glass of water on the sidewalk below, using a very long straw, you would find you can't do it. Why?

 

[Perfection]

And how does the energy get from the air to the walls?

Convection. It's the efficiency of the convection processes that make the conduction the slow step that by and large determines the heat flow out of the house.

Consider the following analogy:

Think of the heat flow like traffic. Convection is an Autobahn, and conduction is a construction detour with a horrific accident where they're down to one lane.

The amount of cars that can go from the autobahn to the detour to the autobahn again isn't determined by the rate at the autobahn, it's the detour that matters.