Heat Transfer and modes of heat transfer
Heat transfer:-
It deals with rate of energy transfer. Energy transfer from one system to another system or from one part of system to another part of system is due to temperature difference is called heat transfer.
Basic cause of heat transfer is temperature difference. Heat transfer helps to predict the temperature distribution.
Modes of heat transfer:-
there are three modes of heat transfer:
- Conduction
- Convection
- Radiation
Conduction
Thermal conduction is a process by which heat transferred from a region of higher temperature to a region of lower temperature within a medium. In conduction, heat transferred from one part to another part of a body through molecular collisions, without any flow of matter.
Gases are poor thermal conductors and solid have high conductivity while liquids have conductivity between gases and solid.
Here are five daily life examples of conduction:
- Cooking on a Stovetop: When you place a pot or pan on a hot stovetop, the heat is conducted from the burner to the cookware, allowing you to cook food.
- Holding a Metal Spoon in Hot Coffee: As mentioned earlier, when you stir your hot coffee with a metal spoon, the heat from the coffee is conducted to the spoon, making it warm.
- Walking Barefoot on a Sunny Sidewalk: On a sunny day, a concrete or asphalt sidewalk can become quite hot. When you walk on it barefoot, heat is conducted from the surface to your feet.
- Touching a Cold Windowpane: During winter, if you touch a cold windowpane, heat is conducted from your hand to the cold glass, making it feel chilly.
- Ironing Clothes: When you use an iron to press your clothes, the heat is conducted from the iron’s soleplate to the fabric, removing wrinkles through conduction.
Convection
Convection is the process of heat transfer by the actual motion of fluid (liquids and gases) over the surface due to temperature difference. Convection can be forced of natural.
Here are five daily life examples of convection:
- Boiling Water: When you boil water in a pot, the hot water rises to the surface while cooler water moves down, creating a convection current.
- Room Heating: In a room with a heating system, warm air rises near the heater, circulates through the room, and then cools as it sinks, creating a convection current that helps distribute heat.
- Cooking: When you cook food in a pan, the hot air near the bottom of the pan rises, and cooler air moves in to replace it, helping to cook the food evenly.
- Ocean Currents: Ocean currents are driven by convection. Warm water near the equator rises, flows towards the poles, cools, and then sinks, creating a continuous circulation of water.
- Hot Air Balloons: Hot air balloons work on the principle of convection. The air inside the balloon is heated, making it less dense than the surrounding air, causing the balloon to rise.
Radiation
Radiation is the transmission of heat in the form of radiant energy or wave motion from one body to another body. In radiation no medium is required. Any body above 0 kelvin emits the radiation.
Here are five daily life examples of radiation:
- Sunlight: Sunlight is a common source of natural radiation. It includes visible light, ultraviolet (UV) rays, and other forms of electromagnetic radiation.
- Microwaves: Microwave ovens use electromagnetic radiation in the microwave frequency range to heat and cook food.
- X-Rays: Medical imaging, like X-rays, uses ionizing radiation to create images of the inside of the body to diagnose and treat various medical conditions.
- Radio Waves: Radio waves are a form of non-ionizing radiation used in radio and television broadcasting, as well as for wireless communication (Wi-Fi, cell phones).
- Smoke Detectors: Some smoke detectors use a small amount of radioactive material, such as americium-241, to detect smoke and trigger an alarm.
Note- conduction and convection are not possible in vacuum but radiation is possible in vacuum.
Frequently Asked Questions:
1. Heat transfer takes place according to
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2. The heat of sun reaches to us according to
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3. In case of liquids and gases, the heat transfer takes place according to
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4. The heat is transferred by conduction, convection and radiation in
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5. the process of heat transfer from one particle of the body to another by the actual motion of heated particle, is called
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6. As the temperature increases, the thermal conductivity of a gas
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7. Thermal conductivity is the maximum for which?
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8. Radiation can heat
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9. In which process, the rate of transfer of heat is maximum ?
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10. Heat transfer occurs due to ______ difference.
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