Your car has been setting out in the hot summer sun all day. The metal hood, the glass windshield, and the fabric upolstry are all at 180 degrees farenheit. If you touch the hood with your hand it could be burned, if you touch the windshield it will be very hot, if you touch the seat it will be very warm. Why is there a difference in how the different objects feel if they are all the same temperature?
The rate at which the materisl can transfer heat to your hand is proportional to k/(density*C), where k is the thermal conductivity. This parameter is called the "thermal diffusivity". The steel hood has the highest thermal diffusivity. Glass is the lowest.
The fabric absorbs most of the heat but the glass window and the metal hood cannot absorb the heat as well as the seat. This is why the fabric feels warm, but the glass window and the metal hood are very hot.
The difference in how the different objects feel, even though they are all at the same temperature, can be explained by understanding the concept of thermal conductivity. Thermal conductivity refers to the ability of a material to conduct heat.
In this case, the metal hood and the glass windshield have high thermal conductivity, meaning they can easily transfer heat. When you touch them, heat is rapidly conducted from the object to your hand, making it feel very hot.
On the other hand, the fabric upholstery has low thermal conductivity. Although it is at the same temperature as the metal hood and the glass windshield, it does not conduct heat as efficiently. Therefore, when you touch the fabric upholstery, the heat transfer is slower, and it may feel warm rather than hot.
Additionally, perception of temperature also depends on other factors such as the specific heat capacity of the material, which determines how much heat energy is required to raise the temperature of the object. Different materials have different specific heat capacities, so even if they are at the same temperature, they may feel different when touched.
In summary, the difference in how the different objects feel is due to variations in thermal conductivity and specific heat capacity, which affect the rate and efficiency of heat transfer when in contact with your hand.