# Quiz 1. Basic Of Thermodynamics – Online Mechanical Quiz

Attempt this 15 questions related to Thermodynamics .You Can check your answer by clicking show answer button and to solve next question click on next button

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#### 1. Which of the following variables controls the physical properties of a perfect gas

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Detailed ans : We know the equation of perfect gas is PV=MRT hence perfect gas depends on pressure ,volume as well as temperature

#### 2.Which law states that the internal energy of a gas is a function of temperature

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Detailed ans : Joule's Law of internal Energy=The principle that at constant temperature the internal energy of an ideal gas is independent of volume. Real gases change their internal energy with volume as a result of intermolecular forces

#### 3.The amount of heat required to raise the temperature of 1 kg of water through 1°C is called

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Detailed ans : kilocalorie - a unit of heat equal to the amount of heat required to raise the temperature of one kilogram of water by one degree at one atmosphere pressure; used by nutritionists to characterize the energy-producing potential in food.

#### 4.The efficiency and work ratio of a simple gas turbine cycle are

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etailed ans : A boiler feed pump needs to be able to deliver feed-water at a higher pressure than the operating pressure of the boiler. ALL of that energy needs to be subtracted from the energy output of the boiler. In addition, you have to consider losses at the mud drum (blow-downs to purge contaminants) radiative heat losses (boiler-houses are pretty hot) and the minor losses involved in de-superheating the steam so that it arrives at the turbine at an optimal temperature to be used at its highest mechanical efficiency. Well-designed turbines have many, many stages at which the latent heat of vaporization can be exploited, including extraction and re-injection, and eventually using the steam in stages that are below atmospheric pressure.

#### 5) The amount of heat required to raise the temperature of the unit mass of gas through one degree at constant volume, is called

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Detailed ans : The constant pressure specific heat is related to the constant volume value by CP = CV + R. The ratio of the specific heats γ = CP/CV is a factor in adiabatic engine processes and in determining the speed of sound in a gas.

#### 6) Workdone in a free expansion process is

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Detailed ans : Free expansion is an irreversible process in which a gas expands into an insulated evacuated chamber. It is also called Joule expansion. During free expansion, no work is done by the gas. The gas goes through states that are not in thermodynamic equilibrium before reaching its final state, which implies that one cannot define thermodynamic parameters as values of the gas as a whole. For example, the pressure changes locally from point to point, and the volume occupied by the gas (which is formed of particles) is not a well defined quantity.

#### 7) Stirling and Ericsson cycles are

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Detailed ans : The Thermodynamic Ericsson cycle was invented by John Ericsson after carrying out research on a number of heat engines developed by him. The Ericsson cycle can be best compared to the Stirling cycle. The Ericsson cycle is the thermodynamic cycle invented by John Ericsson after he built many heat engines. The Ericsson engine working on the principle of Ericson cycle comprises of the regenerator and the heat exchanger. The efficiency of regenerative Ericsson and Stirling engines have been found to be almost the same as Carnot engine, however, the amount of work developed with gas as the working fluid has been found to be insufficient due to low thermal conductivity of gas.

#### 8. The sum of internal energy (U) and the product of pressure and volume (p.v) is known as

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Detailed ans : Enthalpy is the amount of heat content used or released in a system at constant pressure. Enthalpy is usually expressed as the change in enthalpy. The change in enthalpy is related to a change in internal energy (U)) and a change in the volume (V), which is multiplied by the constant pressure of the system.

#### 9) According to Kelvin-Planck's statement of second law of thermodynamics,

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Detailed ans : • The Zeroth Law deals with thermal equilibrium and provides a means for measuring temperatures. • The First Law deals with the conservation of energy and introduces the concept of internal energy. • The Second Law of thermodynamics provides with the guidelines on the conversion heat energy of matter into work. It also introduces the concept of entropy. • The Third Law of thermodynamics defines the absolute zero of entropy. The entropy of a pure crystalline substance at absolute zero temperature is zero.

#### 10. The compression ratio for Diesel engines is

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Detailed ans : Compression ratio is higher than petrol engine in case od compression engine because here carburator is not provided to air fuel mixing . In addition spark plug is absent . To increase the temperature of air fuel mixture in diesel engine higher compression ration is kept high.

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#### 12. The measurement of a thermodynamic property known as temperature is based on

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Detailed ans : • The Zeroth Law deals with thermal equilibrium and provides a means for measuring temperatures. • The First Law deals with the conservation of energy and introduces the concept of internal energy. • The Second Law of thermodynamics provides with the guidelines on the conversion heat energy of matter into work. It also introduces the concept of entropy. • The Third Law of thermodynamics defines the absolute zero of entropy. The entropy of a pure crystalline substance at absolute zero temperature is zero.

#### 13) When the gas is cooled at constant pressure,

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Detailed ans : Isobaric - the pressure is kept constant. An example of an isobaric system is a gas, being slowly heated or cooled, confined by a piston in a cylinder. The work done by the system in an isobaric process is simply the pressure multiplied by the change in volume.

#### 14) The temperature at which the volume of a gas becomes zero is called

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Detailed ans : The temperature at which the volume of an ideal gas becomes zero; a theoretical coldest temperature that can be approached but never reached. Absolute zero is zero on the Kelvin scale, -273.15°C on the Celsius scale, and -459.67°F on the Fahrenheit scale.

#### 15. The heating of gas at constant volume is governed by

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Basic of Thermodynamics Online Objective Quiz
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