Question

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 < TcB) Qh > Qc and Th < TcC) Qh < Qc and Th > TcD) Qh > Qc and Th > Tc

Answer 1

Answer: option D

Explanation: let us first define an heat engine.

An heat engine is that device that converts partly heat energy into mechanical energy.

Inside the heat engine is a substance that undergoes compression and expansion, intake and outtake of heat, this is known as a working substance.

For heat engines to work perfectly, the working substance has to take a substantial large amount of heat energy from a source, this source is the hot reservoir, the amount of heat energy given out by this reservoir is Qh and the temperature at this region is Th. The heat from the hot reservoir is accepted by the working substances and sent to a region that will discard it out, this region is known as the cold reservoir and the heat energy at this point is Qc and temperature is Tc.

Judging by the direction of heat flow, heat energy moves from hot reservoir to the cold reservoir for the heat engine to work perfectly fine, hence Qh must be greater than Qc and Th must be greater than Tc.

Hence Qh>Qc and Th>Tc