← Physics (0625)
Q1 / 5
Transfer of thermal energy
Higher
2 marks
Why does a vacuum flask keep liquids hot or cold?
A
Vacuum between walls stops conduction and convection; silvered walls reflect radiation back; stopper reduces top loss
B
Thick glass walls conduct very poorly
C
Flask uses electrical heating to maintain temperature
D
Only radiation is prevented — conduction and convection are unaffected
Need a hint?