physicshelpline - Question of the day , Thermal Physicsphysicshelpline - Question of the day , Thermal Physicshttps://www.physicshelpline.com/Question/thermal-physicsSat, 20 Jun 2026 13:41:21 +0530http://zoho.com/sites/<![CDATA[Change in Entropy ]]>https://www.physicshelpline.com/Question/post/change-in-entropy

Q- One mole of an ideal gas is contained in a thermally insulated container that is connected to another container of equal volume that is initially evacuated. The valve connecting the two containers is now opened and the gas allowed to expand isothermally to fill both sides. The new total volume is twice original volume.

a) What is the entropy change for this process?

b) Is this process reversible or irreversible? Why? 


Solution:

]]>Fri, 10 Apr 2026 19:13:00 +0530<![CDATA[Conduction and radiation of heat]]>https://www.physicshelpline.com/Question/post/conduction-and-radiation-of-heat

Q- An iPod is left running inside a thin insulating case 2.5 mm thick with thermal conductivity of 0.02 W/K/m. The case is black and at 25 degrees Celsius and exchanges energy with it's surroundings, all of which are at 20 degrees Celsius, by radiation alone. What is the temperature inside the case?

Solution:

]]>Fri, 20 Feb 2026 08:47:55 +0530<![CDATA[Efficiency of an Engine]]>https://www.physicshelpline.com/Question/post/efficiency-of-an-engine

Q- One mol of an ideal monatomic gas is used as the working substance in an engine. The engine operates on the cycle shown in the diagram. Processes BC and DA are reversible and adiabatic. What is the efficiency of the engine? 

Solution:

]]>Sun, 21 Dec 2025 22:28:51 +0530