Question 257: Thermodynamics & KTG

Question

In $$1^{	ext {st }}$$ case, Carnot engine operates between temperatures $$300 \mathrm{~K}$$ and $$100 \mathrm{~K}$$. In $$2^{	ext {nd }}$$ case, as shown in the figure, a combination of two engines is used. The efficiency of this combination (in $$2^{	ext {nd }}$$ case) will be :

Accepted Answer

$${\eta _{net}} = {{{W_1} + {W_2}} \over {{Q_1}}}$$
$${\eta _{net}} = {{{W_1}} \over {{Q_1}}} + {{{W_2}} \over {{Q_1}}}$$
$${\eta _{net}} = {\eta _1} + {{{W_2}} \over {{Q_2}}} 	imes {{{Q_2}} \over {{Q_1}}}$$
$${\eta _{net}} = {\eta _1} + ({\eta _2})(1 - {\eta _1})$$
$$1 - {\eta _1} < 1$$
$$ \Rightarrow {\eta _{net}} < {\eta _1} + {\eta _2}$$

Answer

same as the $$1^{	ext {st }}$$ case.

Answer

always greater than the $$1^{	ext {st }}$$ case.

Answer

always less than the $$1^{	ext {st }}$$ case.

Answer

may increase or decrease with respect to the $$1^{	ext {st }}$$ case.

Thermodynamics & KTG

In $1^{\text {st }} case, Carnot engine operates between temperatures 300 \mathrm{~K} and 100 \mathrm{~K}. In 2^{\text {nd }} case, as shown in the figure, a combination of two engines is used. The efficiency of this combination (in 2^{\text {nd }}$ case) will be :

Choose the correct answer: