Heat is a form of energy which is transferred from a substance having higher temperature to a substance having lower temperature. Addition of heat to a substance increases its internal temperature. Heat is defined as the net amount of thermal energy of a system.
Heat energy is produced due to the motion of subatomic particles like atoms, ions and molecules to solids, gases and liquids. Heat transfer occurs from one system to another system due to the temperature difference between the two systems.
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All forms of matter contain heat energy. No matter if it is a volcano or an ice cube, it has some amount of heat.
There are different forms of energy in nature like mechanical energy, sound energy, light energy, electric energy, tidal energy, heat energy, etc. Heat energy is generated due to the transfer of heat from a warm system to a cool system. Heat energy is an essential form of energy on our day to day activities like cooking, heating, ironing, etc. An object or system from which heat energy is obtained is called a source of heat energy. Here are some of the major sources of heat energy is mentioned below:
The sun, a part of the solar system, is the ultimate source of heat energy for Earth. Life on Earth is possible only due to the presence of sunlight. The form of energy which is obtained from the sun is called solar energy.
The heat energy which is obtained from earth is called geothermal energy. It can be found in hot water and rocks present underground. Heat is also found in the form of molten rocks and magma, deep inside the Earth's crust.
Air is also an important source of heat energy. It is used for heat pumps for both commercial and residential purposes.
Burning of fuels provides heat energy. Fuel is an energy filled combustible substance, which when burnt generates energy. Wood, coal, kerosene, gasoline, petrol, diesel, oil and charcoal are some common fuels.
Electric energy can be converted into heat energy. Iron, water heater and induction cooker are some of the devices which convert electrical energy into heat energy. This is based on the principle of heating effect of electric current.
There are three ways for the transfer of heat, and they are:
1. Convection- It is a process of heat transfer which occurs due to the actual motion of the particles. It usually occurs in liquids and gases. When air gets heated; it becomes hot and carries heat energy. Warm air has less density as compared to cool air, hence warm air rises above and cool air descends below to fill the space. This cool air further becomes warm and rises. This process continues and produces convection current.
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2. Conduction- It is the process of heat transfer which occurs due to the vibration of the molecules about their mean position. Conduction occurs from one part of a system to another part, or in two systems which are in contact with each other. Due to closely packed molecules, solids conduct heat better than liquids and gases.
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3. Radiation- It is a method of heat transfer which uses electromagnetic waves (infrared waves) to transfer heat from one place to the other. This process does not require any medium to transfer heat. Hot objects radiate out heat waves in all directions at the speed of light. When heat waves strikes with an object, it either reflects or absorbs the wave.
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If the constituent particle of an object becomes excited by gaining energy, the particle moves or vibrates rapidly and the object is said to be hot. While, if the particles have less energy it will not vibrate, and the object is said to be cold. Heat is the transfer of energy between these objects due to a difference in temperature.
Here are some examples of heat energy:
● Sun is the biggest source of heat energy in our solar system. It radiates heat, which reaches Earth in the form of radiation.
● A stovetop acts as a source of heat energy when it burns the gas. Anything which is placed above the stove also becomes a source of energy to cook things.
● Automobile fuels are also a source of heat energy. When the fuel burns, it provides energy for the motion of the vehicle.
● A hot cup of tea or coffee contains heat energy.
● When you hold a piece of ice in your palm, the heat energy from your hand melts the ice.
● A radiator, heating system or a room heater provides the necessary radiant heat energy to warm your house during the winter season.
● Conventional oven is a source of convection heat energy; the food becomes hot when it is placed in it.
1. What are some uses of heat energy?
Ans- Some uses of heat energy are mentioned below:
a. Thermometers use heat energy to measure temperature
b. Heat energy is necessary for the existence of life on earth
c. The steam thermal power plant use heat energy to heat the air, and water present in air is also heated
d. Sweater uses heat energy to keep the body warm, by trapping heat between its layers
e. Heat energy melts helps the fuse wire, in fuses, thus preventing any damage to electric circuits
f. Heat energy is used for medication in heat therapy to cure muscle strains
2. How is heat produced?
Ans- Heat is produced by various sources.
The heat energy of the sun is generated due to the fusion of its hydrogen and helium atoms. This energy is then radiated out from the surface of the sun.
The heat energy of a fire is generated due to the combustion of fuel or other materials.
The heat energy of an electric appliance is generated due to the friction of electrons with the resisting elements.
Heat is produced in our body due to the chemical and biological reactions that occur within the cells.
Heat is also produced due to the vibration of the molecules or atoms.