A heat engine is designed to do work. This is possible only if certain relationships between the heats and temperatures at the input and output hold true. Which of the following sets of statements must apply for the heat engine to do work?

A) Qh < Qc and Th < Tc
B) Qh > Qc and Th < Tc
C) Qh < Qc and Th > Tc
D) Qh > Qc and Th > Tc

Part B
Find the work W done by the "ideal" heat engine.
Express W in terms of Qh and Qc
W=_

Part C
The thermal efficiency e of a heat engine is defined as follows: e = W/Qh
Express the efficiency in terms of Qh and Qc.
e=__

The heat engine is the engine that transforms heat (Q) in work (W), and by the second law of the thermodynamics, its efficiency can not be 100%, it means that some heat must be dissipated.

Part A:

The engine works with two sources of heat, one hot (Qh) at a hot temperature (Th) and another cold (Qc) at a cold temperature (Tc). It is necessary so, the hot source will give energy to the fluid of the engine, and the cold source will be the source where these heat will dissipate and the fluid will return to its original temperature. So,

Qh > Qc, and Th > Tc

Part B:

The ideal heat engine is the one that can use the most amount of heat to transform it at work. It is characterized by Qh/Qc = Th/Tc.

The work is the useful energy, so it is the total heat (Qh) less the heat dissipated (Qc):

W = Qh - Qc

Part C:

The effiency is the useful energy divided by the total energy. Because W = Qh - Qc:

e = W/Qh

e = (Qh - Qc)/Qh

e = Qh/Qh - Qc/Qh

e = 1 - Qc/Qh

AFOKE88 AFOKE88 · Answer 2 · 2021-12-10T00:30:56+01:00

A) The statement must apply for the heat engine to do work is; D) Qh > Qc and Th > Tc

B) The work W done by the "ideal" heat engine.

Express W in terms of Qh and Qc is; W = Qh - Qc

C) The thermal efficiency E of a heat engine is; e = 1 - (Qc/Qh)

A) From first law of thermodynamics, when applied to engines, there are two sources of heat which are cold reservoir and hot reservoir. The energy from the hot source is Qh with a temperature Th that is hot.

In contrast, the second source is cold with energy as Qc and a cold temperature of Tc.

Since one is hot and the other is cold, it means that temperature of hot is always more than that of the cold one and as well the energy from the hot one will be greater than that of the cold one. Thus;

Qh > Qc and Th > Tc

B) Qh is the heat absorbed from the hot reservoir after a given time period

Qc is the heat expelled to the cold reservoir.

Therefore net work done by the engine during a specific time period will be:

W = Qh - Qc

C) Formula for thermal efficiency is;

e = (Qh - Qc)/Qh

This will reduce to;

e = 1 - (Qc/Qh)

Read more about first law of thermodynamics at; https://brainly.com/question/15071682