Chapter 11, Problem 1CQ

To determine

The heat engines among the motor engines.

Answer to Problem 1CQ

choice (a) an automobile engine and (c) a steam turbine.

Explanation of Solution

In heat engine, conversion of energy occurs from thermal energy to mechanical energy. The mechanical output from heat engine can be used to do mechanical work. The heat engine will not be 100%. Thus, some of the energy will be released into the low temperature reservoir of the medium. Thus, the total energy input will be the sum of work done and the heat exhausted.

Write an expression for the heat input from the hot reservoir,

$Q_h=Q_c+W$

Here,

$Q_h$ is the heat input

$Q_c$ is the work done

$W$ is the heat exhausted

Conclusion:

In an automobile, an internal combustion engine is developing heat internally.  This heat is converted into mechanical work. Since the heat is developed internally, extraction of heat from an external source does not occur. Thus, choice (a) is correct.

The steam turbine has an external combustion engine. Here, the engine obtains the energy to produce the superheated steam from heating outside of the turbine. Thus, choice (c) is correct.

In electrical motors, conversion of electrical energy to work occurs. Thus, choice (b) is incorrect.