Physics of junior high school Heat transfer problem, junior high school physics Definition, occurren

Is the temperature of any object equal to the temperature at room temperature? It should depend on whether the object itself produces heat and how hot the object itself is. For example, if an object with a temperature higher than the outside temperature produces the same amount of heat in the same amount of time, then its temperature should remain the same, that is, it should always be higher than the outside world; If an object produces more heat than it transfers to the outside world in the same amount of time, then its temperature will become higher and higher.

In both cases, heat transfer takes place, but the temperature of the object is not the same as the outside temperature.

I touched the coins on the table and it felt cold

Because the temperature of your human body is higher than the long temperature, you will feel that there is a temperature difference. If you pinch the coin in your hand for a while, you will feel less cool, because there is heat transfer between your hand and the coin (metal is a good conductor of heat), and part of the internal energy emitted by your person is transferred to the coin, so you will feel that the coin is hot.

The temperature of any object at room temperature is equal to the temperature of its own room temperature.

I touched the coin on the table, but it felt cold, because your body temperature was higher than the coin, and there was a heat transfer between your body and the coin.

That's because your body temperature is higher than the temperature of the coin, and there is a heat transfer between you and the coin.

Normal temperature is a specific temperature of 20 degrees Celsius.

Another longer temperature is room temperature, which is also a specific temperature value: 25 degrees Celsius people feel cold because people's feelings of cold and warmth are determined by people's heat dissipation, as long as the heat on the person can be dissipated, then people feel cold. When you take a walk, you feel hot.

The general body temperature of a person is 37 degrees Celsius, so people will feel cold when they touch things.

Heat transfer can only be carried out if there is a temperature difference. Heat is transferred from a hot object to a cold object. Under the same structural conditions, the larger the temperature difference, the faster the heat transfer.

Touching a coin is cool because the metal has good thermal conductivity, which quickly transfers the heat on your hand, and there is no heat on your hand, so you will feel cold.

The temperature of any object at room temperature is equal to the temperature of its own room temperature.

Heat transfer:

1. Definition: It is the process of heat transfer from a high-temperature object to a low-temperature object, or from the high-temperature part of an object to the low-temperature part. Heat transfer is a natural phenomenon that is prevalent in nature.

2. Conditions: As long as there is a [temperature difference] between objects or between different parts of the same object, there will be heat transfer phenomena, and it will continue until the temperature is the same.

3. Essence: To change the internal energy of an object by means of heat transfer, that is, a part of the internal energy of an object is transferred to another.

objects, or internal energy transfers from the high temperature part of the same object to the low temperature part. (internal energy transfer process).

In the process of heat transfer, the matter does not migrate, but the hot object emits heat, the temperature decreases, the internal energy decreases (to be precise, the average kinetic energy of the molecules in the object does irregular motion decreases), the low temperature object absorbs heat, the temperature increases, and the internal energy increases. Therefore, the essence of heat transfer is the process of transferring energy from a hot object to a low temperature object, which is a way of energy transfer. It is the internal energy that is transferred by heat transfer, not the temperature.

In junior high school, the definition and essence of heat transfer are generally not fully understood. First of all, heat itself is a phenomenon of luminescence and heat, and then this phenomenon is transmitted through radiation, convection, conduction, etc., which is nothing more than whether the transmission efficiency is high or not, and the essence is nothing.

A long time ago, textbooks included "Heat Transfer: Thermal Expansion" as a separate chapter, introducing some basic knowledge of heat transfer and thermal expansion. The current editions of the textbook do not include thermal expansion and heat transfer as a separate chapter, but only introduce a little knowledge of heat transfer when learning "the way to change internal energy" in the ninth grade.

When learning Chapter 13 "Heat and Energy", the junior high school physics of the People's Education Edition learns some knowledge of heat transfer.

Heat transfer: The phenomenon of heat transfer from a high-temperature object to a low-temperature object or from a high-temperature part of an object to a low-temperature part is called heat transfer.

There are three ways in which heat is transferred:

1. Heat conduction: heat is transferred along the object.

2. Thermal convection: Heat transfer by the flow of liquid or gas.

3. Thermal radiation: heat is emitted outward in the form of electromagnetic radiation.

Conditions for heat transfer: temperature difference.

The essence of heat transfer: the transfer of internal energy.

Thermal expansion: Generally, objects expand when heated and shrink when cold. (0-4 water has anti-expansion).

Under the same conditions, the gas expands the maximum and the solid expands the least.

:1 1:2 The specific heat capacity is the property of the substance, which is only related to the material material, and has nothing to do with the mass, so it is 1:1 by J=CMT, that is, C1M1T1=C2M2T2 substituting T1:T2=1:2

2. Waste heat of exhaust gas.

3. d The methods of changing the internal energy are work and heat transfer, and the internal energy is increased only when the ice is heated a. b Heat transfer is not considered. c No consideration is given to the work. d cooled down, did not do external work, internal energy decreased.

4. D The methods of changing internal energy include work and heat transfer, which must be something, it is wrong, and it may be something right.

5. Know the specific heat capacity of the liquid, assuming that it is c, and J=CM(T1-T2) is substituted.

m= specific heat capacity of water if the liquid is water (kg· ) Substitution. m=

For the same material, it can be understood that internal energy is used to express the average speed of molecular thermal motion, and internal energy is the energy of molecular thermal motion.

The heat transfer is also the transfer of internal energy, and the result of the transfer is, of course, that the average velocity of the molecules tends to be the same, that is, the average kinetic energy of all the molecules in the hot and cold objects is finally reached.

Of course, it is the transfer of energy from a hot object to a cold object.

The contact between a low-temperature object and a high-temperature object, and the collision of molecules makes the molecular movement of the low-temperature object more intense and the internal energy increases.

During the transfer, the theorem of conservation of energy is observed, i.e., the total internal energy is constant.

In contact with a high-temperature object, the increase in temperature makes the molecular motion of the low-temperature object more intense, and the internal energy increases, which is one of the aspects. On the other hand, objects are generally thermally expanding and contracting, the temperature increases, the volume will increase, the gap between molecules will increase, and the potential energy of the molecules will also increase.

There are two ways in which heat is transferred between objects: work, heat transfer. There are three pathways of heat transfer: heat conduction, convection, and radiation.

To do work, for example, there is a piston at one end of a closed container, the external force compresses the piston, and the external force does work w joules, then the gas in the container can increase w joules. The heat transfer is more direct, and there should be something like that in the book:

Heat transfer is the process by which heat is transferred from a hot object to a low temperature object, or from a hot part of an object to a low temperature. Heat transfer is a natural phenomenon that is prevalent in nature. As long as there is a temperature difference between objects or between different parts of the same object, the phenomenon of heat transfer will occur and will continue until the temperature is the same.

The only condition for heat transfer to occur is the presence of a temperature difference, regardless of the state of the objects, whether the objects are in contact with each other or not. The result of heat transfer is the disappearance of the temperature difference, i.e. the same temperature is achieved between objects or different parts of the object where heat transfer occurs.

PS: Don't complicate simple problems, junior high school should not have very high requirements for internal energy.

Internal energy is the sum of the kinetic energy and potential energy of the molecule, it is the change of temperature and volume that increases the internal energy, because the object has the property of thermal expansion and contraction, so when the high temperature object transmits the temperature to the low temperature object, the molecular movement of the low temperature object is violent, the volume increases, and the internal energy increases.

Temperature is a measure of the kinetic energy of a molecule, and the higher the temperature, the greater the kinetic energy of the molecule. Internal energy includes molecular kinetic energy and potential energy, and a high-temperature object transfers heat to a low-temperature object, even though the molecular kinetic energy of a low-temperature object increases!