Transfer of heat from a body with a higher body temperature to a body with a lower body temperature is defined as heat conduction. Transfer of heat is broadly classified into three different categories, namely, conduction, convection, and radiation. Out of these three, conduction is the process that exists in all three states of matter. Heat conduction is an invisible phenomenon, as it doesn’t involve the real displacement of the particles of caloric energy. It is basically the transfer of internal thermal energy that occurs by the collisions of high-speed microscopic particles to slow-speed particles, which in turn increases the speed/kinetic energy of slow-moving particles. Buring a flame, ironing clothes, stirring hot food, and hot compress to muscles are the most common examples of heat conduction in day-to-day life. The rate of conduction can be defined as-
Q/t = kA (T_{2}–T_{1})/dΒ Β
where,
- Q = transfer of heat per unit of time
- K = thermal conductivity of the body
- A = the area of heat transfer
- T_{hot} = the temperature of the hot region
- T_{cold} = the temperature of the cold region
- d = thickness of the body
EXAMPLES OF HEAT CONDUCTION
There are numerous daily life applications that tend to demonstrate the process of conduction of heat in real life. Some examples of such applications are given below:
1. Stirring Hot Food
When we stir the hot food with a conductive material, like a spoon, we feel the heat at the end of the stirrer/spoon. This happens because of the heat conduction process. To reduce this effect, nowadays insulators, such as wood, rubber, and plastic, are used at the end of some utensils.
2. Heating an Iron Rod
Heating an iron rod is the most convenient and easiest way to understand the process of conduction. In this process, one end of the conductor rod is placed in contact with direct heat due to which heat energy gets coupled from the heat source to the rod. Without the real displacement ofΒ particles, heat conduction is observed from one particle to another reaching the end of the rod.
3. Iron Chair And Wooden Chair
If an iron chair and a wooden chair are kept in direct exposure to sunlight and observed for some time, one can observe that the iron chair absorbs more heat than the wooden one. This is because iron is a good conductor of heat, while wood is an insulator. Therefore, iron chair gets heated easily when exposed to sunlight.
4. From the hand to an ice cube
Ice cubes, when placed on a person’s hand melt faster. This happens because of the transfer of heat energy from the skin surface to ice cubes.
5. Motor and Engine
The heating up of motors, engines and other mechanical devices after some time of operation is a significant example of conduction in everyday life. Motors and engines are usually made up of conducting materials, such as iron, copper, steel, aluminum, steel, etc., and the energy released from motors and engines is in the form of heat. This released heat radiate into the surroundings and gets coupled to the device particles, which heats up the machinery.
6. Electric Iron
The electric irons use the conduction property for their basic operation. The current supplied to the electric iron passes through the internal circuitry of the device, and the lower surface of the iron gets heated up. The heat gets evenly spread throughout the surface of the iron due to the process of heat conduction.
7. Ovens
The inner surface of the ovens is made up of metals or conducting materials. The conduction property of the metals allows the heat to spread evenly throughout the oven to cook food.
8. Thermos Flask
A thermos flask, an electronic equipment, is a liquid storage device that is used to maintain the temperature of a liquid for a long duration of time. This means that the cold liquid poured into the thermos will remain cool and the hot liquid will remains hot for a specific time. A thermos flask is also based on conduction for its basic operation. A conducting material is used to manufacture this equipment so as to lock the conduction of heat.
9. From one person to another
When people hug, heat transfer takes place from the person with a higher body temperature to the person with a lower body temperature.
10. From the hand to a piece of chocolate
If we hold a bar of chocolate in our hands for a long time, it will melt because of the heat transfer from the hands to the chocolate.
11. Hot compresses to muscles
Hot water bags are used to relax muscles so as to get rid of pain. It also works on the conduction phenomenon as the heat transfer takes place from the compressor/hot water bag to the skin and from there to the muscles.
12. From a hot cup to our hands
When a hot beverage is kept in the hands for some time, the conduction of heat occurs from the cup to the hands making the hands warm. That’s why in winter people prefer hot beverages.
13. From a flame to our skin
If we are standing close to the flame for a long time, the heat will get transferred to our skin surface causing it to burn. Heat transfer takes place without the direct contact of the particles, therefore it is an example of heat conduction.
14. From the stones to our skin
Stones absorb the heat from sunlight, therefore if we touch a stone that is kept under direct exposure to sunlight for a long duration will transfer heat to our skin surface causing a burning sensation on our skin.
15. From drinks to ice
When ice cubes are added to a beverage, heat conduction from drinks to ice takes place making ice thaw.