Question

Engines are rated at specified conditions. Then which of the following statements are correct?

1. Power developed increases as local temperature increases.

2. Power developed increases as local temperature decreases

3. Power developed is not dependent on local temperature.

4. Power developed increases as local atmospheric pressure increases.

5. Power developed increases as local atmospheric pressure decreases.
1. 1 and 4
2. 3 and 4
3. 3 and 5
4. 2 and 4

Answer 1

Correct Answer - Option 4 : 2 and 4

Concept:

The burning capacity of the engine depends on combustion power of oxygen. In hilly areas, where local atmospheric pressure is less, the density of air is reduced which means that less oxygen is available for combustion due to which power developed by engines is reduced. Therefore, Power developed decreases as local atmospheric pressure decreases and vice versa.

The density of air reduces on increasing the temperature because at higher temperature mean free path between gas molecules increases, which further implies that less oxygen is available for combustion due to which power developed by engines is reduced. Therefore, Power developed reduces as local temperature increases and vice-versa.