Question

Explain carnot's cycle for heat engine with P-V diagram.​

Answer 1

Answer:

As the engine works, the working substance of the engine undergoes a cycle known as Carnot cycle.

Explanation:

(i) First Step : Isothermal expansion curve AB. The cylinder with gas is allowed to expand slowly at constant temperature T1 by putting in on the source.

Work done = heat absorbed by the system.

(ii) Second Step : Adiabatic expansion the cylinder is kept on the insulating stand while still expanding the gas (adiabatic) till the temperature falls to 7.

(iii) Third Step : Isothermal compression, the cylinder is placed on the sink and the gas is compressed at constant temperature.

Answer 2

Answer:

Carnot's cycle  for heat engine was introduced by Saddy Carnot. Tt is completely theoretical, ideal and reversible heat engine. The efficiency of Carnot's engine is theoretically possible maximum value that a engine can have.    

Explanation:

Construction : Cylinder is containing a working substance placed on source(at high temperature).Then , there is sink which is at low temperature. It contains four processes.

• Isothermal Expansion: When the load on the piston (placed on the cylinder) is decreased. Working substance expands. Internal energy will decrease caused decreased in temperature. Since the system in the contact with source. So it will absorb q₁ heat from the source. System will remain at constant temperature.

                            ΔU = q + w    

     ⇒                        q = -w                                   [∵ΔU = 0]

                            $q_{1}=-W_{AB}=RT_{H} ln\frac{V_2}{V_1}$                    

• Adiabatic expansion: Cylinder is removed from the source, again put on the insulating pad. So, the load is decreased further, to cause the expansion adiabatically(q=0).

                                 ΔU =  $W_{BC}=C_{V} (T_{H}-T_{C} )$                

        Due to expansion the internal energy of the system decreased and temperature decreased.

• Isothermal Compression: Cylinder is transferred to sink and load increased on the piston again, to cause the compression. Internal energy and temperature increased.

               ∴                    ΔU=0 and ΔT=0

                            $q_{2} =-W_{CD} = RT_{c} ln\frac{V_{4} }{V_{3} }$

• Adiabatic compression: Cylinder is transferred to insulating pad load is increased to cause adiabatic compression. Due to compression temperature decreased.(q=0)
•                            ΔU =$W_{DA}=C_{V} (T_{C}-T_{H} )$

         Net work done,  $W_{net}=W_{AB}+W_{BC}+W_{CD}+W_{DA}$

                                   $W_{net}= -R(T_{H}-T_{c}) ln\frac{V_2}{V_1}$

• Efficiency of the Carnot's engine,

                          η  = $\frac{work done}{heat supplied} =\frac{T_{H}-T_c}{T_H}$