39 real Thermodynamics questions from the Mechanical Core bank, as asked in Indian campus drives and tech interviews. Every question has a verified answer and an AI-tutor explanation on placd — free to start.
1. What is Zeroth law?
Junior
A.two systems each in thermal equilibrium with a third are in equilibrium with each other, the principle that lets a thermometer define temperature
B.four equalities among partial derivatives of pressure, volume, temperature and entropy, letting an unmeasurable entropy derivative be replaced by measurable quantities
C.cyclic integral of δQ/T is zero for a reversible cycle and negative for an irreversible one, a test of whether a proposed cycle is possible
D.the ratio of the actual molar volume of a gas to that predicted by the ideal gas law, equal to one for an ideal gas
2. Which term means: "two systems each in thermal equilibrium with a third are in equilibrium with each other, the principle that lets a thermometer define temperature"?
A.Zeroth law — four equalities among partial derivatives of pressure, volume, temperature and entropy, letting an unmeasurable entropy derivative be replaced by measurable quantities
B.Zeroth law — two systems each in thermal equilibrium with a third are in equilibrium with each other, the principle that lets a thermometer define temperature
C.Zeroth law — no cyclic device can receive heat from a single reservoir and convert all of it into work
D.Zeroth law — constant-enthalpy expansion across a restriction with no work or heat transfer, used in refrigerant expansion valves and the porous-plug experiment
A.First law for a cycle — maximum useful work obtainable from a system as it comes to equilibrium with the dead state of its surroundings
B.First law for a cycle — the entropy of an isolated system can never decrease, staying constant only for a reversible process
C.First law for a cycle — net heat transferred to a system over a cycle equals the net work done by it, which establishes internal energy as a property
D.First law for a cycle — the ratio of the actual molar volume of a gas to that predicted by the ideal gas law, equal to one for an ideal gas
A.Kelvin-Planck statement — two systems each in thermal equilibrium with a third are in equilibrium with each other, the principle that lets a thermometer define temperature
B.Kelvin-Planck statement — bleeding steam from the turbine to preheat boiler feedwater, raising the mean temperature of heat addition and hence Rankine cycle efficiency
C.Kelvin-Planck statement — 1 − TL/TH, the upper limit for any heat engine between two reservoirs, depending only on their absolute temperatures
D.Kelvin-Planck statement — no cyclic device can receive heat from a single reservoir and convert all of it into work
11. Which term means: "cyclic integral of δQ/T is zero for a reversible cycle and negative for an irreversible one, a test of whether a proposed cycle is possible"?
A.Clausius inequality — bleeding steam from the turbine to preheat boiler feedwater, raising the mean temperature of heat addition and hence Rankine cycle efficiency
B.Clausius inequality — maximum useful work obtainable from a system as it comes to equilibrium with the dead state of its surroundings
C.Clausius inequality — cyclic integral of δQ/T is zero for a reversible cycle and negative for an irreversible one, a test of whether a proposed cycle is possible
D.Clausius inequality — four equalities among partial derivatives of pressure, volume, temperature and entropy, letting an unmeasurable entropy derivative be replaced by measurable quantities
A.Carnot efficiency — 1 − TL/TH, the upper limit for any heat engine between two reservoirs, depending only on their absolute temperatures
B.Carnot efficiency — rate of change of temperature with pressure at constant enthalpy, positive when a gas cools on expansion below its inversion temperature
C.Carnot efficiency — no device can transfer heat from a colder to a hotter body as its sole effect, without some other input
D.Carnot efficiency — maximum useful work obtainable from a system as it comes to equilibrium with the dead state of its surroundings
A.Exergy — maximum useful work obtainable from a system as it comes to equilibrium with the dead state of its surroundings
B.Exergy — bleeding steam from the turbine to preheat boiler feedwater, raising the mean temperature of heat addition and hence Rankine cycle efficiency
C.Exergy — no cyclic device can receive heat from a single reservoir and convert all of it into work
D.Exergy — net heat transferred to a system over a cycle equals the net work done by it, which establishes internal energy as a property
20. Which term means: "constant-enthalpy expansion across a restriction with no work or heat transfer, used in refrigerant expansion valves and the porous-plug experiment"?
A.Throttling process — no device can transfer heat from a colder to a hotter body as its sole effect, without some other input
B.Throttling process — four equalities among partial derivatives of pressure, volume, temperature and entropy, letting an unmeasurable entropy derivative be replaced by measurable quantities
C.Throttling process — 1 − TL/TH, the upper limit for any heat engine between two reservoirs, depending only on their absolute temperatures
D.Throttling process — constant-enthalpy expansion across a restriction with no work or heat transfer, used in refrigerant expansion valves and the porous-plug experiment
A.constant-enthalpy expansion across a restriction with no work or heat transfer, used in refrigerant expansion valves and the porous-plug experiment
B.no device can transfer heat from a colder to a hotter body as its sole effect, without some other input
C.four equalities among partial derivatives of pressure, volume, temperature and entropy, letting an unmeasurable entropy derivative be replaced by measurable quantities
D.rate of change of temperature with pressure at constant enthalpy, positive when a gas cools on expansion below its inversion temperature
23. Which term means: "rate of change of temperature with pressure at constant enthalpy, positive when a gas cools on expansion below its inversion temperature"?
A.Joule-Thomson coefficient — 1 − TL/TH, the upper limit for any heat engine between two reservoirs, depending only on their absolute temperatures
B.Joule-Thomson coefficient — no device can transfer heat from a colder to a hotter body as its sole effect, without some other input
C.Joule-Thomson coefficient — constant-enthalpy expansion across a restriction with no work or heat transfer, used in refrigerant expansion valves and the porous-plug experiment
D.Joule-Thomson coefficient — rate of change of temperature with pressure at constant enthalpy, positive when a gas cools on expansion below its inversion temperature
26. Which term means: "bleeding steam from the turbine to preheat boiler feedwater, raising the mean temperature of heat addition and hence Rankine cycle efficiency"?
A.Regenerative feed heating — four equalities among partial derivatives of pressure, volume, temperature and entropy, letting an unmeasurable entropy derivative be replaced by measurable quantities
B.Regenerative feed heating — 1 − TL/TH, the upper limit for any heat engine between two reservoirs, depending only on their absolute temperatures
C.Regenerative feed heating — bleeding steam from the turbine to preheat boiler feedwater, raising the mean temperature of heat addition and hence Rankine cycle efficiency
D.Regenerative feed heating — no device can transfer heat from a colder to a hotter body as its sole effect, without some other input
A.four equalities among partial derivatives of pressure, volume, temperature and entropy, letting an unmeasurable entropy derivative be replaced by measurable quantities
B.cyclic integral of δQ/T is zero for a reversible cycle and negative for an irreversible one, a test of whether a proposed cycle is possible
C.1 − TL/TH, the upper limit for any heat engine between two reservoirs, depending only on their absolute temperatures
D.no device can transfer heat from a colder to a hotter body as its sole effect, without some other input
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