The question asks for the primary function of a thermos flask. We need to recall the basic principle and design of a thermos flask to identify its main purpose.
C) To maintain the temperature of liquids — This accurately describes the primary function of a thermos flask, which is to insulate its contents from the external environment, thereby preserving their temperature.
The question asks about the primary principle a thermos flask uses to maintain temperature. A thermos flask is designed to minimize heat transfer between its contents and the surroundings. We need to identify which heat transfer mechanism it primarily counters.
Correct Option: C) Insulation. A thermos flask primarily uses the principle of insulation to maintain temperature. Insulation is the process of preventing heat transfer, which a thermos flask achieves by minimizing conduction, convection, and radiation through its design (vacuum, reflective surfaces, and insulating stopper).
The question asks about the primary modes of heat transfer prevented by the vacuum in a thermos flask. We need to understand how heat is transferred and how a vacuum affects these processes.
A) Conduction and convection. The vacuum between the walls of a thermos flask effectively eliminates the medium required for both conduction and convection, thus preventing heat transfer by these two methods.
The question asks about the material commonly used for the inner lining of a thermos flask. A thermos flask is designed to minimize heat transfer to keep its contents hot or cold. This involves understanding the principles of heat transfer: conduction, convection, and radiation. The inner lining plays a crucial role in reducing heat loss or gain.
A) Glass — The inner lining of a thermos flask is typically made of glass, which is then silvered. The silvered surface is highly reflective, minimizing heat transfer by radiation. Glass itself is also a poor conductor of heat, further contributing to the flask's insulating properties.
The question asks to identify the inventor of the thermos flask. This is a factual recall question related to scientific inventions and their inventors. We need to associate the invention with the correct scientist.
B) James Dewar is credited with inventing the thermos flask (also known as the vacuum flask) in 1892. He developed it as a scientific tool to maintain the temperature of its contents by minimizing heat transfer through conduction, convection, and radiation.
The question asks about the surface treatment of the inner bottle of a thermos flask. A thermos flask is designed to minimize heat transfer. Heat can be transferred by conduction, convection, and radiation. We need to consider how each of these modes of heat transfer is addressed in the design of a thermos flask, specifically focusing on the outer surface of the inner bottle.
B) Polished — A polished or silvered surface is highly reflective and a poor emitter of thermal radiation. By polishing the outer surface of the inner bottle, heat radiated from the hot liquid inside is reflected back, and heat from the outside is reflected away, thus minimizing heat transfer by radiation across the vacuum.