Question

A gasoline engine operates at a temperature of 270°C and exhausts at 210°C. Calculate the maximum efficiency of this engine. (Note that the Celsius scale is used.)

89.0 %
88.0 %
12.0 %
11.0 %

Answer 1

Given:

Th = 270 °C = 270+273 = 543 K, hot temperature

Tc = 210 °C = 210+273 = 363 K, cold temperature

According to the Carnot theorem, the maximum efficiency achievable by a heat engine between a hot and cold temperature is

η = 1 - Tc/Th

= 1 - 363/543

= 0.668 = 11.047 (approx)

Answer: 11.0% (nearest integer)

Answer 2

Hello! the efficiency of a thermal engine depends on how much of the initial input is transformed into work, Here 270°c is the input and 210°c is the output.

Then the efficiency is calculated as e = 1 - Tc/Th, where Th is the hot temperature (in this case 270°C) and Tc is the cold temperature (in this case 210°C)

First we need to write the temperatures in kelvin degrees, this can be done by adding 273.15 to the celsius scale:

Th = 270 + 273.15 = 543.15

Tc = 210 +273.15 = 483.15

then the efficiency is e = 1 - 543.15/483.15 = 0.11

if we write this as a percentage, we get an efficiency of 11%, then the fourth answer is the correct one.