# Homework Help: Thermometer touching the floor and a carpet

1. Oct 25, 2014

### Karol

1. The problem statement, all variables and given/known data
A thermometer touches the floor and the other touches a wool carpet lying on the floor. what will the two thermometers show, the same or different temperatures

2. Relevant equations
Two materials touching each other the heat moves from the warm to the cold one

3. The attempt at a solution
I heard that the thermometer won't feel the heat if it doesn't pass to it. so, is it true that if i touch a warm isolating material like a ceramic brick with a thermometer it won't show the real temperature?

2. Oct 25, 2014

### haruspex

Is it true that a ceramic brick completely blocks all transfer of heat?

3. Oct 25, 2014

### Karol

no, of course not, only vacuum blocks heat transfer by conduction, but i might feel the brick colder than it really is, if i touch it by hand or apply a thermometer to it

4. Oct 26, 2014

### haruspex

So suppose you put a thermometer, initially at 20C, on a ceramic tile at 30C and wait. What will happen?

5. Oct 26, 2014

### Karol

well, with time the thermometer will show 30C

6. Oct 26, 2014

### haruspex

Exactly. The thermometer will still show the temperature of the object eventually, but if the object is made of an insulating material there may be some delay. Does this answer your original question?

7. Oct 26, 2014

### Karol

well, maybe it answers. but if i touch a very hot ceramic brick, will i feel it's real temperature, will i be burned or not? because the heat transfer is slow.

8. Oct 26, 2014

### haruspex

This is a bit different because you have a lot more thermal capacity than a thermometer has. Instantaneously it should feel pretty hot, but then the region close to you finger cools a bit because of the heat lost to you, and the heat you absorbed is carried away by your bloodstream. So the heat keeps flowing into you from the brick, but you get rid of it fast enough that your finger stays relatively cool.
This is why people can walk on hot coals.

9. Oct 28, 2014

Thanks