Question

You are a mechanic in a garage and are working on a carburetor that is made of metal, has a glass inspection window and plastic gears for the choke. If all three types of material are at the same temperature and each type of material is in contact with the other two, then
A. heat will flow from the plastic to the glass, and from the glass to the metal.
B. heat will flow from the metal to the glass, and from the glass to the plastic.
C. heat will flow from the glass to both the plastic and the metal.
D. no heat will flow between any parts.

Answer 1

Answer:

The correct option is;

D. no heat will flow between any part

Explanation:

Here, we are required to know the thermal conductivity of the three materials

1. Metal

2. Glass and

3. Plastic

The thermal conductivity of the above materials are

1. Metal e.g Iron = 0.163 cm² C/cm = 79.5 W/(m K)

2. Glass = 0.0025 cm² C/cm = 0.8 W/(m K)

3. Plastic = 0.19 W/(m K)

Therefore due to the very low conductivity of the glass and the plastic, there will be no heat flow between the parts.