A factory in Germany manufactures vacuum flasks for keeping liquids hot or cold. The space between the inner and outer walls of the flask is a vacuum.

What is the main purpose of the vacuum in reducing heat transfer?

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Question

A factory in Germany manufactures vacuum flasks for keeping liquids hot or cold. The space between the inner and outer walls of the flask is a vacuum.

What is the main purpose of the vacuum in reducing heat transfer?

Accepted Answer

To prevent heat loss by conduction and convection only — Award 1 mark for identifying that the vacuum prevents conduction and convection, which require particles. B is incorrect — radiation can travel through a vacuum. C is incorrect — radiation is not prevented by the vacuum. D is incorrect — reflection is achieved by the silvered surfaces, not the vacuum.

Answer

To prevent heat loss by conduction and convection only

Answer

To prevent heat loss by conduction, convection and radiation

Answer

To reflect thermal radiation back into the flask

Answer

To prevent heat loss by radiation only

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