WAEC Physics 2020 Objective — Question 48

Question 48 of 50 from the West African Examinations Council (WAEC) Physics 2020 Objective paper, with the correct answer and a full explanation.

The vacuum between the double walls of a thermos flask reduces heat loss through

A. conduction and radiation
B. convection and conductionCorrect
C. radiation only
D. conduction only

Explanation

Heat loss by conduction is reduced by the vacuum, stopper, glass, cork and air spaces. Heat loss by convection is reduced by the vacuum, stopper and the trapped air spaces. Heat loss by radiation is reduced by the silvered glass walls. The vacuum specifically reduces heat loss through both conduction and convection.

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