[alshaymah]

You are coming in on a very hot summer day and the room is even hotter. The only cool place is the refrigerator. So, you open its door to cool the room. You leave it open for awhile. Will the air in the room be cooler, same temperature, or warmer than before you opened the refrigerator door? Explain.

[Capuchin]

Here you need to take the room as a system, and analyse what's going into and what's coming out of the room.

If you look at it this way, it should be obvious what happens to the temperature in the room.

Let me know if you get an answer. I'll be happy to check it.

[alshaymah]

I think the temprerature of the room will decrease. The cool air will transfer to the hot air till they have similar temperature. But am worry about the word he opnned the frigerator for awhile!?

[Capuchin]

No, you need to think a little more. What is going in and out of the ROOM.

[alshaymah]

The room is closed. The cool air goes down and the hot air goes up.
Mmmmm still confusing. Am I close to the right answer?

[Capuchin]

Well, when you first open the fridge, the air in the fridge and the air outside the fridge mix so the air in the room becomes the average temp of both of those (taking volume differences into account). Then, when that's happened, electricity is coming into the room to power the refrigerator, some of that power must be turned to heat, so the room will gradually get warmer.

[alshaymah]

Oh this is so :D disapointed.
You can't imagine the temperature in my country in summer.

Thank you very much. It was very helpful.

I want to rate your answer it tells me I have to spread something :confused:

[ebaines]

This is why the hot air exhaust of an air conditioner must always be outside of the room you are trying to cool. If you put a window-style air conditioner in the middle of a room and turn it on, the average temp of the room would rise.

[alshaymah]

Thank you Capuchin my dear friend :) for your help the answer was totally right.

Thank you ebaines it was very helpful your exblenation.

Regards

[Capuchin]

Thank YOU for entering into a conversation with us in order to find the right answer. So many people who come here put their question then never say thank you or have a stab at it themselves.

If every poster were like you, the world would be a better place :)

[iAMfromHuntersBar]

OK, can I piggyback this question with a similar one I've always wondered about;

If I'm running a bath, with hot water coming out of the tap at 50oC and fill it half full, then turn off the hot water and turn on the cold water, which is at 5oC, until it's full.

Hypothetically, if no heat was lost through steam or other external means, is there a way of me calculating what the heat of the water will be?

[Capuchin]

It will be the mean, pretty much.

[Capuchin]

Here's a curve for 50C water and 5C water, these are the particle energies on x and number of particles with that energy on y, the mean particle energy is the temperature.

The 50C particles all hit the 5C particles and give them extra energy, after a while, the distribution fits the red curve, at 27.5C

[iAMfromHuntersBar]

Cheers Capuchin, I had an incling it might be, but I just thought it would be far more complicated than that!

[Capuchin]

Physics is simple sometimes :)

[alshaymah]

http://img.photobucket.com/albums/v2...Jackie2Dvi.jpg:D

[Capuchin]

Thanks! :D

[asterisk_man]

Hey Capuchin, what program did you use for that awesome graph? Multiple graphs, trend lines, annotations... it looks pretty full featured ;)

[Capuchin]

I could tell you, but there's little point as you wouldn't understand.

[Lowtax4eva]

A fridge works by removing heat from inside of it and dissipating that heat out the coils on the back into the room, opening the door will not change the temperature of the room, the cool out coming out the front will eventually mix with the hot air out the back. All you'll do is burn the motor out cause it won't stop.