Question

2.2.4 quiz: transfer of thermal energy
question 9 of 10
some thermal mugs have layers of materials to keep drinks hot for as long as possible. which combination of layers would work best for this purpose?
a. inner core of glass, air gap, outer layer of plastic
b. inner core of steel, air gap, outer layer of plastic
c. inner core of steel, no air gap, outer layer of glass
d. inner core of steel, no air gap, outer layer of plastic

Explanation:

Air is a poor conductor of heat. An air - gap reduces heat transfer by conduction. Steel is a better conductor of heat than glass. To keep drinks hot for a long time, we want a material with low thermal conductivity for the inner core and an air - gap to minimize heat loss. Glass has lower thermal conductivity than steel, and with an air - gap and an outer plastic layer (which is also a poor conductor), it will be more effective at retaining heat.

Answer:

A. Inner core of glass, air gap, outer layer of plastic