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TOPIC: THERMAL ENERGY
SUB-TOPIC: Heat transfer
Meaning of heat transfer
Thermal energy or heat energy is a form of energy. It is a form of energy that flows from a hot area to a cold one. Heat flow is the flow of heat in an object like iron rod from the area of high temperature to area of low temperature through the medium. Hot body loses heat to a cooler one. Heat can be transferred by three processes: conduction, convection, and radiation.
Conduction: This is the process by which heat energy is transferred from region of high temperature of a body to a lower temperature body along a stationary solid material. it is this process that makes a pot on fire to transfer heat to the handle of a pot, even if only the tip is in the fireplace. This method of heat transfer requires a solid material medium.
Convection: transfers heat through the exchange of hot and cold molecules; this is the process through which water in a kettle becomes uniformly hot even though only the bottom of the kettle contacts the flame. The material medium for this process is liquid and gas only. This is way small amount of hot water can warm a full pocket of cold water.
Radiation: is the transfer of heat via electromagnetic (usually infrared) radiation; this is the principal mechanism through which a fireplace warms a room. This process does not require any material medium but the heat is transferred through a vacuum. This is what enables the heat of the sun to reach us or fire burning far away while we feel the heat somewhere.
Experiment 1,
Title: Heat Flow-Hold a thick piece of copper wire in a Bunsen flame. Can you continue to hold it for long? The end of the wire in the flame becomes hot after a short time. How does the heat get along the wire? The only way in which this can happen is for the heat to be passed on from one particle to the next until it reaches the far end of the wire. Then, we say that heat is conducted, and the process is called Conduction.Only metals can conduct heat, non-metals cannot conduct heat. However, we have good conductors and bad conductors.
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