Friday, December 14, 2007

Conduction, Convection and Radiation

Homework

1) Identify one way in which conduction, convection and radiation are used in the community and industry.

Conduction

An example of conduction in communities is in stoves. When the fire is generated, conducting is used in the metal gauzes on top top of the stove. They are metal so that they will heat quicker and then in turn display conduction again when they heat up the bottom of the metal pot cooking the food.

An example of conduction in industries is electrical wires. The heat/electricity will move through the metal easily because it is a conductor of heat and quickly get to where it needs to go. The rubber surrounding it will not take any of the heat because it is not a conductor.

Convection

An example of convection in industries is a boiler. Conventional boilers burn fuel in a combustion chamber surrounded by a water jacket. This heats the water, which is then circulated around the heating system. Unfortunately, not all the heat produced by the burning fuel is used to heat the water.

Boilers are also used in communitites and households but a more domestic version is used. Another example of convection in communities is in refridgerators. Convection is used in refridgerators to cool them down. Heat is carried away into the plastic around the fridge there fore the back of fridges are always warm.


Radiation

An example of radiation as used in the industry is X-rays. X-rays are a type of radiation. Bones are denser than skin so whenever X-rays are done, bones and other dense materials cast shadows that can be detected on photographic film. It is a fast and easy method for doctors to see patients bones and help them.

An example of radiation in the community is a solar water heater. They use the sun to heat either water or a water transfer fluid in collectors. Hot water systems use a pump to circulate portable water from the water storage tank through one or more collectors and back to the tank. The most common collectors are flat plate collectors. This is a rectangular box with a transparent cover, installed on a building.


2) Give three reasons why an insulated flask can be used to keep things hot and/or cold.

- They are sealed at the edges by melting the edges together. The air is removed from the spaces between the two to produce a vacuum. This vacuum slows down the movement of heat by convection.

– There is a glass bottle placed over the inner compartment. This reflects heat radiation and lessens the loss of heat.

- A rubber or cork seal also prevents heat loss and gain. Also, all materials used in the flask are poor conductors of heat.