Question

A Carnot engine works first between 200°C and 0°C and
then between 0°C and –200°C. The ratio of its efficiency in
the two cases is
(a) 1.0 (b) 0.577
(c) 0.34 (d) 0.68

Answer 1

Answer:

ANSWER

Case 1:

T

1

=0°C=(0+273)K=273K

T

2

=200°=(200+273)K=473K

η

1

=1−

T

2

T

1

=1−

473

273

=0.422

Case 2:

T

1

=−200°C=(−200+273)K=73K

T

2

=0°=(0+273)K=273K

η

2

=1−

T

2

T

1

=1−

273

73

=0.73

Ratio of efficiencies, η

1

:η

2

=0.42:0.73=1:1.73