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Transfer of heat

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meera chavda

There are three main modes of heat transfer: conduction, convection, and radiation. Conduction involves direct contact between objects where heat is transferred through atomic vibrations. Convection involves the transfer of heat by mass motion of molecules in liquids and gases as heated parts rise and cooler parts sink. Radiation transfers heat through electromagnetic waves and does not require a medium, allowing it to occur through a vacuum. Examples of each mode in nature and their uses in applications like cooking and heating are discussed.

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Transfer of heat Conduction, convection, radiation 1 like, share, subscribe, comment- channel meera chavda
Flow of heat • Heat flows from object at higher temperature to the object at lower temperature. • Example1:- large spoon left in hot vessel also becomes hot after some time.becomes hot after some time. • Example 2:- ice cube starts to melt when kept at room temperature because warmer atmosphere transfers its heat to the cold ice and ice melts. 2 like, share, subscribe, comment- channel meera chavda
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Modes of transfer of heat There are three modes of transfer of heat:- 1. Conduction:- Energy is transferred by direct contact. 2. Convection:- Energy is2. Convection:- Energy is transferred by mass motion of molecules. 3. Radiation:- Energy is transferred by electromagnetic radiation. like, share, subscribe, comment- channel meera chavda 4
Conduction • Particles of solids are tightly packed. When one end of solid metal rod is heated, the atoms of that part start to get heated and vibrate. This heat is then passed on to adjacent atom. This process continuous and entire metal rod gets heated. • Good conductors:- the material• Good conductors:- the material which conduct heat easily through them are known as good conductors. Example:- all metals like copper, iron, aluminium. • Bad conductors:- the material which do not conduct heat through them easily are called bad conductors. Example:- wood, brick, plastic, paper, glass, cotton etc. like, share, subscribe, comment- channel meera chavda 5
Conduction • Two important condition for conduction:- 1. There should be temperaturetemperature difference between the two bodies. 2. The two bodies at different temperatures should be in direct contact of each other. like, share, subscribe, comment- channel meera chavda 6
Uses of good and bad conductors • Good conductors like steel, copper are used to make utensils so that they can cook food easily as they transfer good quantity of heat to food • Bad conductors like plastic, wood and Bakelite are used to make handles of utensils. • Bad conductors like wool are used to make winterquantity of heat to food being cooked. • Good conductor like copper or iron are used to make iron base, heater coil, boilers in chemical industry. are used to make winter garments. • Ice is bad conductor hence Eskimos make the igloo of ice. • Bad conductors like thermocol are use to make icebox to carry ice. like, share, subscribe, comment- channel meera chavda 7
Convection • This mode of transfer takes place in liquid and gases. • The particle of liquid or gas gets heated near the source of heat and move upwards. • The space left by them is filled by the cold particles surrounding them. • So, in the process of convection, the heat gets transferred onto a • So, in the process of convection, the heat gets transferred onto a substance by the actual movement of heated particles with in the substance. • Convection cannot take place in solid because their particles are fixed in the respective places and are not free to move within substances. like, share, subscribe, comment- channel meera chavda 8
Convection current in nature Sea breeze • During day time:- - The land absorbs sun’s heat more in comparison to water in sea. So land becomes hotter. - The air above the land becomes hotter compared to Land breeze • During the night:- - The land region looses the heat faster than sea. - The air above the sea is warmer than that above the land. - Thus, the warmer air above the becomes hotter compared to air above the sea. - The hot air from the land rises upwards and the cold air from the sea rush to land to fill the space. - So, the convection current from the ocean to the land causes sea breeze. - Thus, the warmer air above the sea rises upwards. - The cold air from the land rushes towards the sea to fill the space created above the sea. - The convection current from the land to the sea causes land breeze. like, share, subscribe, comment- channel meera chavda 9
Uses of convection current in our lives • Air conditioner are fitted higher in the wall because the cold air generated by them easily moves downwards and cools the room effectively. • The room heaters are place near the floor because the warm air rises upwards and heatsbecause the warm air rises upwards and heats the room effectively. • The freezer inside the refrigerator are surrounded by cooling pipes and have minimum temperature. The freezer is located on top of the refrigerator because the cool air moves downwards and cools freeze effectively. like, share, subscribe, comment- channel meera chavda 10
Radiation • The heat and light energy from the sun travels to the earth through radiation. • The radiation carrying heat energy is called thermal radiation. • Thermal radiation needs no medium. It can travel through vacuum. • The amount of thermal radiation absorbed by an object depends on:- - The nature of material example metals absorb more heat than non-metal. - Its distance from the source of heat:- if the source of heat is near then object will be more medium. It can travel through vacuum. heat:- if the source of heat is near then object will be more hot and if the source of heat is far object will be less hot - Colour of object:- dark colour object absorb more heat and light colour object absorb less heat. like, share, subscribe, comment- channel meera chavda 11
Use of radiation in our daily life • We wear light coloured clothes in summer because light colour absorb minimum heat. • Dark coloured clothes are preferred in winter because they absorb maximum heat from the surrounding. • The bottom of cooking vessel is kept dark in colour so that maximum heat is absorbed from the bottom. • Pipes of solar heater and vessels of solar cooker are painted black so that maximum heat is absorbed from sunlight. like, share, subscribe, comment- channel meera chavda 12
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Transfer of heat

  • 1. Transfer of heat Conduction, convection, radiation 1 like, share, subscribe, comment- channel meera chavda
  • 2. Flow of heat • Heat flows from object at higher temperature to the object at lower temperature. • Example1:- large spoon left in hot vessel also becomes hot after some time.becomes hot after some time. • Example 2:- ice cube starts to melt when kept at room temperature because warmer atmosphere transfers its heat to the cold ice and ice melts. 2 like, share, subscribe, comment- channel meera chavda
  • 3. like, share, subscribe, comment- channel meera chavda 3
  • 4. Modes of transfer of heat There are three modes of transfer of heat:- 1. Conduction:- Energy is transferred by direct contact. 2. Convection:- Energy is2. Convection:- Energy is transferred by mass motion of molecules. 3. Radiation:- Energy is transferred by electromagnetic radiation. like, share, subscribe, comment- channel meera chavda 4
  • 5. Conduction • Particles of solids are tightly packed. When one end of solid metal rod is heated, the atoms of that part start to get heated and vibrate. This heat is then passed on to adjacent atom. This process continuous and entire metal rod gets heated. • Good conductors:- the material• Good conductors:- the material which conduct heat easily through them are known as good conductors. Example:- all metals like copper, iron, aluminium. • Bad conductors:- the material which do not conduct heat through them easily are called bad conductors. Example:- wood, brick, plastic, paper, glass, cotton etc. like, share, subscribe, comment- channel meera chavda 5
  • 6. Conduction • Two important condition for conduction:- 1. There should be temperaturetemperature difference between the two bodies. 2. The two bodies at different temperatures should be in direct contact of each other. like, share, subscribe, comment- channel meera chavda 6
  • 7. Uses of good and bad conductors • Good conductors like steel, copper are used to make utensils so that they can cook food easily as they transfer good quantity of heat to food • Bad conductors like plastic, wood and Bakelite are used to make handles of utensils. • Bad conductors like wool are used to make winterquantity of heat to food being cooked. • Good conductor like copper or iron are used to make iron base, heater coil, boilers in chemical industry. are used to make winter garments. • Ice is bad conductor hence Eskimos make the igloo of ice. • Bad conductors like thermocol are use to make icebox to carry ice. like, share, subscribe, comment- channel meera chavda 7
  • 8. Convection • This mode of transfer takes place in liquid and gases. • The particle of liquid or gas gets heated near the source of heat and move upwards. • The space left by them is filled by the cold particles surrounding them. • So, in the process of convection, the heat gets transferred onto a • So, in the process of convection, the heat gets transferred onto a substance by the actual movement of heated particles with in the substance. • Convection cannot take place in solid because their particles are fixed in the respective places and are not free to move within substances. like, share, subscribe, comment- channel meera chavda 8
  • 9. Convection current in nature Sea breeze • During day time:- - The land absorbs sun’s heat more in comparison to water in sea. So land becomes hotter. - The air above the land becomes hotter compared to Land breeze • During the night:- - The land region looses the heat faster than sea. - The air above the sea is warmer than that above the land. - Thus, the warmer air above the becomes hotter compared to air above the sea. - The hot air from the land rises upwards and the cold air from the sea rush to land to fill the space. - So, the convection current from the ocean to the land causes sea breeze. - Thus, the warmer air above the sea rises upwards. - The cold air from the land rushes towards the sea to fill the space created above the sea. - The convection current from the land to the sea causes land breeze. like, share, subscribe, comment- channel meera chavda 9
  • 10. Uses of convection current in our lives • Air conditioner are fitted higher in the wall because the cold air generated by them easily moves downwards and cools the room effectively. • The room heaters are place near the floor because the warm air rises upwards and heatsbecause the warm air rises upwards and heats the room effectively. • The freezer inside the refrigerator are surrounded by cooling pipes and have minimum temperature. The freezer is located on top of the refrigerator because the cool air moves downwards and cools freeze effectively. like, share, subscribe, comment- channel meera chavda 10
  • 11. Radiation • The heat and light energy from the sun travels to the earth through radiation. • The radiation carrying heat energy is called thermal radiation. • Thermal radiation needs no medium. It can travel through vacuum. • The amount of thermal radiation absorbed by an object depends on:- - The nature of material example metals absorb more heat than non-metal. - Its distance from the source of heat:- if the source of heat is near then object will be more medium. It can travel through vacuum. heat:- if the source of heat is near then object will be more hot and if the source of heat is far object will be less hot - Colour of object:- dark colour object absorb more heat and light colour object absorb less heat. like, share, subscribe, comment- channel meera chavda 11
  • 12. Use of radiation in our daily life • We wear light coloured clothes in summer because light colour absorb minimum heat. • Dark coloured clothes are preferred in winter because they absorb maximum heat from the surrounding. • The bottom of cooking vessel is kept dark in colour so that maximum heat is absorbed from the bottom. • Pipes of solar heater and vessels of solar cooker are painted black so that maximum heat is absorbed from sunlight. like, share, subscribe, comment- channel meera chavda 12