Question

The insulating material is best for domestic refrigerators is

• A. Thermocole
• B. Glass wool
• C. Glass sheet
• D. PUF

Hint:

Polyurethane foam has very low conductivity, resists moisture and is foamed in place in the cabinet wall.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
The walls of a domestic refrigerator need insulation to keep heat out. Good insulation has low thermal conductivity, low moisture absorption and good strength.

Step 2: Key Approach:
We compare the four materials on these properties and on how well they fit thin refrigerator walls.

Step 3: Detailed Explanation:
PUF (polyurethane foam) has a very low thermal conductivity.
It is foamed in place between the inner and outer shell, so it fills every gap.
It resists moisture and gives strength to the cabinet. A thin layer gives good insulation, so more space is left inside.
For these reasons modern domestic refrigerators use PUF.

Step 4: Why the other options are wrong.
Thermocole (expanded polystyrene) is cheap but needs a thicker layer, and it is weaker.
Glass wool absorbs moisture and loses its insulating power.
Glass sheet is a poor insulator and is not used as insulation.

Final Answer:
PUF is the best insulating material for domestic refrigerators. This is option (D).