PhysicsChapter 1: Heat Capacity and Modes of Heat Transfer
Vacuum Flask
Definition
Vacuum Flask
A **vacuum flask** reduces thermal-energy transfer between its contents and surroundings.
Vacuum
The gap between the walls contains very little matter. This strongly reduces: * conduction through the gap; * convection through the gap.
Shiny Walls
Reflective surfaces reduce transfer by thermal radiation.
Stopper
An insulating stopper reduces conduction through the opening and limits air movement.
Narrow Neck
A narrow neck reduces the area available for heat transfer.
Critical Idea
A vacuum does not stop radiation. That is why reflective surfaces are still necessary.
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Sticky Notes · Quick Revision
VACUUM
- Conduction ↓ Convection ↓
SHINY
- Radiation ↓
STOPPER
- Insulator