WHAT is Heat ??
Heat is the energy that is transmitted from one body to another as a result of a temperature change.
Heat energy always flow/get transmitted from a body at high temperature to lower temperature.
Heat is governed by 2nd Law of Thermodynamics that states "heat energy cannot be transferred from a body at a lower temperature to a body at a higher temperature without the addition of energy."
This is why it costs money to run an air conditioner & refrigerators😜.
Example: When you are cooking in kitchen and the stove is ON the flames produced by stove releases heat to the surrounding. This heat is transferred to the vessel placed on it and this in turn transfers the heat to the food in the vessel making it hot. During this process you might have observed that the temperature in the kitchen also rises, No that's not because the fan is turned off but due to the heat generated by flames. The heat released by flames is not only transferred to the vessel but also to the surrounding of the stove and Kitchen by means of radiation. Here since the temperature of the kitchen was lower that that of the Heat it started releasing heat to the surrounding atmosphere also.
S.I Unit : joules ( J )
CGS Unit : Calories ( cal )
WHAT are the modes of heat being transferred ??
Heat is transferred in three mode:
Conduction
Convection
Radiation
HOW does Conduction takes place ??
Conduction is the transfer of heat energy by collisions between adjacent atoms or molecules.
Conduction takes place more easily in solids and liquids when the particles are closer together than in gases because the particles are farther apart.
When there is a significant temperature difference between the substances in contact, the rate of energy transfer by conduction is faster.
The rate of heat transfer on Conduction depends upon following factors:
Geometry of the Medium
it's thickness
material
temperature difference across the medium.
Eg:
The heat from a hot liquid heats up the cup. If you pick up a cup of hot coffee, tea, or broth in it, the cup will be hot, and your hands will feel it.
The iron gets heated up when ironing a piece of fabric, and the heat is passed to the clothing.
If you touch a hot stove, heat will be conducted to your finger and your skin will burn😭.
HOW does Convection takes place ??
Convection is the mechanism of transferring heat by the mass movement of molecules in fluids such as gases and liquids.
The initial heat transfer between the material and the fluid occurs through conduction, but the bulk heat transfer occurs due to fluid motion.
The faster the fluid motion, greater is the convection heat transfer.
In absence of any bulk fluid motion, heat transfer between a solid surface and the adjacent fluid by pure conduction.
Types of Convection:
NATURAL CONVECTION: Fluid motion occurs due to density variations caused by temperature difference is known as free convection. If the fluid motion is caused by the buoyancy forces that re induced by density difference due to the variation of temperature in the fluid.
FORCE CONVECTION: Fluid motion is caused by external agency like Fan, Blower or pump, etc. If the fluid is forced to flow over the object /surface by external means it is called Forced Convection.
Heat Transfer processes that involve change of phase of a fluid is also considered as convection because the fluid motion induced during the process. such as the rise of the vapor bubbles during the boiling or the fall of the liquid droplets during the condensation.
Eg:
Warm-blooded creatures use convection to control their body temperatures, which you probably didn't knew. The human heart is a pump, and blood pumping is an indicator of forced convection in the human body. The heat generated by the cells in the body is transmitted to the air or water flowing over the skin.
The theory of convection is responsible for hot air balloons' ability to rise. You may have seen the heater at the balloon's base. This heater warms the air as it pushes upwards. The hot air that rises becomes trapped within the balloon, causing the balloon to rise as well. When the hot air balloon needs to land, some of the hot air is released by the balloon.
On a hot summer day, air conditioners are frequently turned on. The theory of convection is used in the cooling of air in air conditioners. Cold air is emitted by the air conditioners. Since the cold air is denser than the warm air, it sinks. Hot air rises when it is less dense and is pulled in by the air conditioner.
Did you know most of the ovens utilize the principle of convection? In the case of convection ovens, forced convection is employed. With heating, the molecules present in the air also get heated up and start moving. The food inside the oven is cooked due to this warm air.
HOW does Radiation takes place ??
Radiation is defined as energy or particles emitted by a source and travel across space or other mediums.
All physical matter in the solid, liquid, gaseous state emit thermal radiations in the form of electro-magnetic waves (photons) because of vibrational and rotational movement of the molecules and atoms which make up the matter.
The Radiation is emitted at all temperatures.
All bodies above absolute zero emit thermal radiations.
Unlike Conduction and Convection, the heat transfer through Radiation doesn't require any intervening medium.
In fact, heat transfer by radiation is the fastest and it suffers no attenuation in vacuum.
Eg:
When you are near a bonfire and you feel warm, it's due to radiated heat coming from bonfire.
Even the transfer of heat from Sun to the surface of earth takes place by Radiation.
There are many such examples of radiations that you can find near by you🧐..
Do let us know it the comment section😃.
WHAT is the application/significance if Heat ??
Heat is very important in our daily life in warming the house, cooking, heating the water and drying the washed clothes.
Heat has many usages in the industry as making and processing the food and manufacture of the glass, the paper, the textile, etc.
Heat is used as a simple yet effective way to manage the pain and the joint or muscular stiffness, The deep and penetrating heat does not only relieve the pain but also it enhances the recovery process.
Heat plays a vital role in health care. The heat has the ability to counter inflammation and reduces pain. Hence, heat is used in the treatment of inflammatory and pain-related problems. Drinking hot water during a common cold or cough helps relieve the symptoms.
The water cycle is a phenomenon responsible for the rain and life on earth. When the heat from the sun contacts water on the earth, it evaporates by forming water vapor. This evaporation mostly happens from the oceans to form clouds. In turn, these vaporous clouds reach the land through the sky, get cooled, and cause rains. The rainwater collects in pools, ponds, rivers, etc., and the excess returns to seas and oceans.
Sterilization is a process to kill any microbes in drugs and other healthcare material. This aims to keep the preparation sterile until use. So Heat sterilization is the most common and highly effective method of doing it.
And what not...
Heat has many application in our daily lives. Knowingly or unknowingly we all have used heat energy in some or the manner today itself and are using it right now too !!
So we can conclude that, Heat is one of the most important quantity in our life. We use it throughout the day in different forms and modes. Right from food, clothing and shelter to medicines and therapeutical usages, also metabolism. At the end we just advice you to "Feel the Heat"🥵😜.
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