1) A fask has the following features;
a plastic stopper
glass walls with silver coating on both sides
vacuume between walls
plasic spacer
Which features of the flask reduce energy transfer by:
a) radiation
b) conduction
c) convection
2) Many vacuume flasks have steel walls instead of glass.
a) How would this affect how fast some hot coffee cools?
b) Why do you think steel is used instead of glass?
3) Would the flask keep a cold drink cold on a hot day? Explain your answer.
4) A solar panel for heating water has the following features;
a frame
glass cover
rigid foam
copper pipes
copper plate, painted black on top
aluminium plate
fibreglass insulation
Explain the design of the solar panel that are intended to:
a) Let infrared radiation go through
b) Absorb infrared radiation
c) Reflect infrared radiation.
5) Explain why a desert fox's large ears help to keep it cool.
6) Describe two adaptations the artic fox has for living in a cold climate.
7) Explain why air moving over a object can increase its rate of cooling.
8) Explain how and why partsd of the solar panel are designed to reduce heat transfer by convection, conduction and radiation.
This is a discussion question. I will be happy to critique your response.
Please try your own answers first I am sure you can come up with some answers.
soggy ballbags on your face
1) To understand how the features of the flask reduce energy transfer, we should consider the different types of energy transfer.
a) Radiation is the transfer of thermal energy through electromagnetic waves. The silver coating on both sides of the glass walls reduces radiation by reflecting the waves back into the flask instead of allowing them to escape.
b) Conduction is the transfer of thermal energy between objects in direct contact. The plastic stopper and plastic spacer act as poor conductors and minimize heat transfer by conduction.
c) Convection is the transfer of thermal energy through the movement of a fluid, like air or liquid. The vacuum between the glass walls disrupts the flow of air or fluid, preventing convection from occurring and reducing heat transfer by convection.
2) If vacuum flasks have steel walls instead of glass, several factors may change:
a) Steel is a better conductor of heat compared to glass, so a vacuum flask with steel walls may cool hot coffee faster. This is because the steel walls will allow more heat to flow through them compared to glass walls.
b) Steel is used instead of glass in some vacuum flasks because it offers better durability and resistance to impacts. This makes the flask more suitable for outdoor activities or situations where durability is a priority.
3) The flask would indeed keep a cold drink cold on a hot day. The same principles that reduce energy transfer by radiation, conduction, and convection also work in reverse. The plastic stopper and spacer, silver-coated glass walls, and vacuum between the walls inhibit the entry of external heat and the escape of internal cold, effectively insulating the cold drink from the hot ambient temperature.
4) Let's examine the features of the solar panel to understand how they serve their intended purposes:
a) The glass cover of the solar panel is transparent to infrared radiation, allowing it to pass through and reach the underlying components.
b) The copper plate, painted black on top, is designed to absorb infrared radiation. Black surfaces are efficient absorbers of radiation, including infrared, which allows the copper plate to absorb the incoming radiation energy.
c) The aluminium plate is included to reflect infrared radiation. Aluminium has high reflectivity, and by being placed on top of the copper plate, it helps prevent the escape of absorbed radiation, reflecting it back towards the copper plate.
5) A desert fox's large ears help keep it cool through a process called thermoregulation. The ears have a large surface area compared to the rest of the body, enabling greater heat dissipation. As the fox moves or air blows over its ears, the increased surface area facilitates the transfer of heat from the body to the surroundings, cooling the fox.
6) The arctic fox has several adaptations to survive in a cold climate:
- Thick fur and warm undercoat provide insulation and help retain body heat.
- Small, rounded ears help reduce heat loss by minimizing the surface area exposed to cold winds and freezing temperatures.
7) When air moves over an object, it increases the rate of cooling through a process called forced convection. As the air flows past the object's surface, it carries away the heat through convection more rapidly than if the air were still. This increased air movement enhances the transfer of heat from the object to the surrounding air, resulting in faster cooling.
8) The various parts of the solar panel are designed to reduce heat transfer by convection, conduction, and radiation.
- The fibreglass insulation helps minimize heat transfer by conduction by acting as a thermal barrier, preventing direct contact between the copper pipes, plate, and other components.
- The rigid foam also serves as insulation, reducing heat transfer by conduction.
- The glass cover allows sunlight, including infrared radiation, to pass through, minimizing the loss of radiant energy from the panel.
- The design of the frame aims to hold all the components securely in place and does not play a significant role in reducing heat transfer by convection or radiation.