The correct answer is [D] Conduction, convection, and radiation. A thermos flask is designed to minimize heat loss through all three mechanisms. The vacuum between the inner and outer walls of the flask effectively prevents heat transfer by conduction and convection. Since there is no medium for theRead more
The correct answer is [D] Conduction, convection, and radiation. A thermos flask is designed to minimize heat loss through all three mechanisms. The vacuum between the inner and outer walls of the flask effectively prevents heat transfer by conduction and convection. Since there is no medium for these processes to occur in the vacuum, they are significantly reduced. To tackle heat loss through radiation, the inner surfaces of the flask are usually coated with a reflective material like aluminum. This reflective coating helps to reflect infrared radiation back into the liquid, maintaining its temperature. The combination of these features ensures that the thermos flask is highly efficient at keeping its contents hot or cold for extended periods. By addressing all three methods of heat transfer, the thermos flask exemplifies a practical application of thermal insulation principles, making it an essential tool for preserving the temperature of liquids.
The correct answer is [A] Dewar. Sir James Dewar, a Scottish scientist, is credited with inventing the Thermos flask in 1892. Dewar was a chemist and physicist known for his work in cryogenics and the study of low-temperature phenomena. He created the vacuum flask, or Dewar flask, as part of his resRead more
The correct answer is [A] Dewar. Sir James Dewar, a Scottish scientist, is credited with inventing the Thermos flask in 1892. Dewar was a chemist and physicist known for his work in cryogenics and the study of low-temperature phenomena. He created the vacuum flask, or Dewar flask, as part of his research on the liquefaction of gases. The design involved placing one glass bottle inside another and evacuating the air between them, creating a vacuum that significantly reduced heat transfer by conduction and convection. This innovation was essential for maintaining substances at stable temperatures for extended periods. Although Dewar invented the flask, he did not patent it. Later, the German company Thermos GmbH commercialized the design, leading to the product being commonly known as the Thermos flask. The invention has since become a staple in both scientific laboratories and everyday use for keeping liquids hot or cold.
Option C: Food gets cooked in less time in a pressure cooker because high pressure increases the temperature of boiling water. When water boils under high pressure inside the pressure cooker, its boiling point rises above the normal 100°C (212°F). This elevated temperature speeds up the cooking procRead more
Option C: Food gets cooked in less time in a pressure cooker because high pressure increases the temperature of boiling water. When water boils under high pressure inside the pressure cooker, its boiling point rises above the normal 100°C (212°F). This elevated temperature speeds up the cooking process significantly. As the pressure cooker’s sealed environment traps steam generated from boiling water, it creates high pressure, forcing the water to reach temperatures higher than its normal boiling point. These increased temperatures facilitate faster cooking by effectively transferring heat energy to the food inside. The higher temperature and pressure inside the pressure cooker also help break down tough fibers in foods like meats, resulting in tender and flavorful dishes in a shorter time. Option A is incorrect because high pressure raises, rather than reduces, the temperature of boiling water. Option B is inaccurate; although the sealed environment prevents air from entering or escaping, the main factor for faster cooking is the increased temperature due to high pressure. Option D is also incorrect; while reduced evaporation does occur in a pressure cooker, it’s not the primary reason for faster cooking. Therefore, the correct explanation is option C, as high pressure increases the temperature of boiling water, leading to quicker cooking times in a pressure cooker.
Option B: Energy is produced in the Sun by nuclear fusion. In the Sun's core, hydrogen nuclei (protons) fuse together to form helium nuclei through a process called nuclear fusion. This fusion reaction releases tremendous amounts of energy in the form of light and heat. The fusion process involves tRead more
Option B: Energy is produced in the Sun by nuclear fusion. In the Sun’s core, hydrogen nuclei (protons) fuse together to form helium nuclei through a process called nuclear fusion. This fusion reaction releases tremendous amounts of energy in the form of light and heat. The fusion process involves the conversion of mass into energy according to Einstein’s famous equation, E=mc², where a small amount of mass is converted into a large amount of energy. This energy is what powers the Sun and sustains its luminosity and heat output.
Nuclear fusion occurs under the extreme temperature and pressure conditions found in the Sun’s core, where hydrogen atoms are squeezed together with enough force to overcome their natural repulsion and fuse into helium atoms. This process releases a significant amount of energy in the form of gamma rays, which are eventually converted into visible light as they travel outwards through the Sun’s layers.
Options A (nuclear fission), C (oxidation reactions), and D (reduction reactions) are incorrect because they do not accurately describe the process by which energy is generated in the Sun. Nuclear fission involves the splitting of heavy atomic nuclei, while oxidation and reduction reactions typically involve the transfer of electrons between atoms, neither of which is the primary mechanism for energy production in the Sun. Therefore, option B, nuclear fusion, is the correct answer.
Option C: Dynamo converts mechanical energy into electrical energy. A dynamo consists of coils of wire rotating within a magnetic field. When the coils rotate, they cut through the magnetic field lines, inducing an electromotive force (EMF) according to Faraday's law of electromagnetic induction. ThRead more
Option C: Dynamo converts mechanical energy into electrical energy. A dynamo consists of coils of wire rotating within a magnetic field. When the coils rotate, they cut through the magnetic field lines, inducing an electromotive force (EMF) according to Faraday’s law of electromagnetic induction. This EMF causes a flow of electrons, generating electrical current. In essence, the mechanical energy used to rotate the coils is converted into electrical energy. This process is commonly seen in devices like electric generators and bicycle dynamos, where mechanical motion, such as the rotation of a turbine or the movement of bicycle wheels, is harnessed to produce electricity. Option A (high voltage into low voltage) is incorrect, as dynamos typically produce electricity at a relatively low voltage, which can then be transformed to higher voltages using transformers. Option B (electrical energy into mechanical energy) is incorrect, as that describes the operation of an electric motor, not a dynamo. Option D (low voltage into high voltage) is incorrect because dynamos generate electricity rather than transforming voltage levels. Therefore, option C accurately describes the function of a dynamo in converting mechanical energy into electrical energy through electromagnetic induction.
Heat loss in a thermos flask can be prevented by
The correct answer is [D] Conduction, convection, and radiation. A thermos flask is designed to minimize heat loss through all three mechanisms. The vacuum between the inner and outer walls of the flask effectively prevents heat transfer by conduction and convection. Since there is no medium for theRead more
The correct answer is [D] Conduction, convection, and radiation. A thermos flask is designed to minimize heat loss through all three mechanisms. The vacuum between the inner and outer walls of the flask effectively prevents heat transfer by conduction and convection. Since there is no medium for these processes to occur in the vacuum, they are significantly reduced. To tackle heat loss through radiation, the inner surfaces of the flask are usually coated with a reflective material like aluminum. This reflective coating helps to reflect infrared radiation back into the liquid, maintaining its temperature. The combination of these features ensures that the thermos flask is highly efficient at keeping its contents hot or cold for extended periods. By addressing all three methods of heat transfer, the thermos flask exemplifies a practical application of thermal insulation principles, making it an essential tool for preserving the temperature of liquids.
See lessThe inventor of Thermos Flask is
The correct answer is [A] Dewar. Sir James Dewar, a Scottish scientist, is credited with inventing the Thermos flask in 1892. Dewar was a chemist and physicist known for his work in cryogenics and the study of low-temperature phenomena. He created the vacuum flask, or Dewar flask, as part of his resRead more
The correct answer is [A] Dewar. Sir James Dewar, a Scottish scientist, is credited with inventing the Thermos flask in 1892. Dewar was a chemist and physicist known for his work in cryogenics and the study of low-temperature phenomena. He created the vacuum flask, or Dewar flask, as part of his research on the liquefaction of gases. The design involved placing one glass bottle inside another and evacuating the air between them, creating a vacuum that significantly reduced heat transfer by conduction and convection. This innovation was essential for maintaining substances at stable temperatures for extended periods. Although Dewar invented the flask, he did not patent it. Later, the German company Thermos GmbH commercialized the design, leading to the product being commonly known as the Thermos flask. The invention has since become a staple in both scientific laboratories and everyday use for keeping liquids hot or cold.
See lessFood gets cooked in less time in a pressure cooker, because
Option C: Food gets cooked in less time in a pressure cooker because high pressure increases the temperature of boiling water. When water boils under high pressure inside the pressure cooker, its boiling point rises above the normal 100°C (212°F). This elevated temperature speeds up the cooking procRead more
Option C: Food gets cooked in less time in a pressure cooker because high pressure increases the temperature of boiling water. When water boils under high pressure inside the pressure cooker, its boiling point rises above the normal 100°C (212°F). This elevated temperature speeds up the cooking process significantly. As the pressure cooker’s sealed environment traps steam generated from boiling water, it creates high pressure, forcing the water to reach temperatures higher than its normal boiling point. These increased temperatures facilitate faster cooking by effectively transferring heat energy to the food inside. The higher temperature and pressure inside the pressure cooker also help break down tough fibers in foods like meats, resulting in tender and flavorful dishes in a shorter time. Option A is incorrect because high pressure raises, rather than reduces, the temperature of boiling water. Option B is inaccurate; although the sealed environment prevents air from entering or escaping, the main factor for faster cooking is the increased temperature due to high pressure. Option D is also incorrect; while reduced evaporation does occur in a pressure cooker, it’s not the primary reason for faster cooking. Therefore, the correct explanation is option C, as high pressure increases the temperature of boiling water, leading to quicker cooking times in a pressure cooker.
See lessEnergy is produced in the Sun by
Option B: Energy is produced in the Sun by nuclear fusion. In the Sun's core, hydrogen nuclei (protons) fuse together to form helium nuclei through a process called nuclear fusion. This fusion reaction releases tremendous amounts of energy in the form of light and heat. The fusion process involves tRead more
Option B: Energy is produced in the Sun by nuclear fusion. In the Sun’s core, hydrogen nuclei (protons) fuse together to form helium nuclei through a process called nuclear fusion. This fusion reaction releases tremendous amounts of energy in the form of light and heat. The fusion process involves the conversion of mass into energy according to Einstein’s famous equation, E=mc², where a small amount of mass is converted into a large amount of energy. This energy is what powers the Sun and sustains its luminosity and heat output.
Nuclear fusion occurs under the extreme temperature and pressure conditions found in the Sun’s core, where hydrogen atoms are squeezed together with enough force to overcome their natural repulsion and fuse into helium atoms. This process releases a significant amount of energy in the form of gamma rays, which are eventually converted into visible light as they travel outwards through the Sun’s layers.
Options A (nuclear fission), C (oxidation reactions), and D (reduction reactions) are incorrect because they do not accurately describe the process by which energy is generated in the Sun. Nuclear fission involves the splitting of heavy atomic nuclei, while oxidation and reduction reactions typically involve the transfer of electrons between atoms, neither of which is the primary mechanism for energy production in the Sun. Therefore, option B, nuclear fusion, is the correct answer.
See lessDynamo converts
Option C: Dynamo converts mechanical energy into electrical energy. A dynamo consists of coils of wire rotating within a magnetic field. When the coils rotate, they cut through the magnetic field lines, inducing an electromotive force (EMF) according to Faraday's law of electromagnetic induction. ThRead more
Option C: Dynamo converts mechanical energy into electrical energy. A dynamo consists of coils of wire rotating within a magnetic field. When the coils rotate, they cut through the magnetic field lines, inducing an electromotive force (EMF) according to Faraday’s law of electromagnetic induction. This EMF causes a flow of electrons, generating electrical current. In essence, the mechanical energy used to rotate the coils is converted into electrical energy. This process is commonly seen in devices like electric generators and bicycle dynamos, where mechanical motion, such as the rotation of a turbine or the movement of bicycle wheels, is harnessed to produce electricity. Option A (high voltage into low voltage) is incorrect, as dynamos typically produce electricity at a relatively low voltage, which can then be transformed to higher voltages using transformers. Option B (electrical energy into mechanical energy) is incorrect, as that describes the operation of an electric motor, not a dynamo. Option D (low voltage into high voltage) is incorrect because dynamos generate electricity rather than transforming voltage levels. Therefore, option C accurately describes the function of a dynamo in converting mechanical energy into electrical energy through electromagnetic induction.
See less