Thermodynamics important questions

Question No 1 :

The following are examples of some intensive and extensive properties :

1. Pressure
2. Temperature
3. Volume
4. Velocity
5. Electronic charge
6. Magnetisation
7. Viscosity
8. Potential energy

Which one of the following sets gives the correct combinations of Intensive and Extensive properties?

Option A : Intensive - 1 2 3 4 Extensive - 5 6 7 8

Option B : Intensive - 1 3 5 7 Extensive - 2 4 6 8

Option C : Intensive - 1 2 4 7 Extensive - 3 5 6 8

Option D : Intensive - 2 3 6 8 Extensive - 1 4 5 7

Explanation : 

Intensive properties : Independent of mass 

Extensive properties : Dependent of mass 

Question No 2 :

In an isothermal process, internal energy?

Option A: Increases

Option B: Decreases 

Option C: Remain constant

Option D: Gradually increases

Explanation: Decreases

Question No 3 : 

A reversible process?

Option A: Must pass through a continuous series of equilibrium states

Option B: Leaves no history of the events in surroundings 

Option C: Must pass through the same states on the reversed path as on the forward path 

Option D: All of these

Explanation: All of the above

Question No 4 : 

The specific heat of water with rising of temperature?

Option A: Increases

Option B: Decreases 

Option C: First decreases to a minimum then increases

Option D: Remain constant 

Explanation: Decrease to a minimum first then increase 

Question No 5 : 

When two bodies are in thermal equilibrium with a third body, they are also in thermal equilibrium with each other. This statement is :

Option A: Zeroth law of thermodynamics 

Option B: First law of thermodynamics 

Option C: Second law of thermodynamics 

Option D: None of the above 

Explanation: This is the statement of the zeroth law of thermodynamics 

Question No 6 : 

Kelvin-Plank's law deals with?

Option A: Conversion of work into heat

Option B: Conversion of heat into work 

Option C: Conversion of work 

Option D: Conversion of heat 

Explanation: Conversion of heat into work 

Question No 7 : 

According to the kinetic theory of gases, at absolute zero?

Option A: Specific heat of molecules reduces to zero 

Option B: Volume of gas reduce to zero

Option C: Kinetic energy of molecules reduces to zero 

Option D: Pressure of gas reduces to zero 

Explanation: Kinetic energy of molecules reduces to zero 

Question No 8 :

In a throttling process?

Option A : W = 0 

Option B : H = 0 

Option C : E = 0 

Option D : All of the above 

Explanation : At throttling all W, H, E = 0 

Question No 9 : 

In all reversible process, the entropy of the universe?

Option A: Increases 

Option B: Decreases 

Option C: Remains the same 

Option D: None of the above 

Explanation: Increases

Question No 10 : 

Efficiency of Carnot cycle is given by :

Option A : T1 + T2 / T1 

Option B : T1 - T2 / T1 

Option C : T1 / T1 + T2

Option D : T1 / T1 - T2 

Explanation : T1 - T2 / T1 

Question No 11 : 

The Carnot cycle consists of two reversible adiabatic processes and 

Option A: Two reversible isothermal processes 

Option B: Two reversible constant pressure processes 

Option C: Two reversible constant volume processes 

Option D: One reversible constant pressure processes

Explanation: Two reversible isothermal processes

Question No 12 : 

Carnot cycle has maximum efficiency for?

Option A : Petrol engine 

Option B : Diesel engine 

Option C : Reversible engine 

Option D : Irreversible engine 

Explanation : Reversible engine 

Question No 13 :

In the Carnot cycle, the algebraic sum of the entropy changes for the cycle is?

Option A: Positive

Option B: Negative 

Option C: Zero 

Option D: None of the above 

Explanation: Zero 

Question No 14 : 
In the Carnot cycle, the process carried at extremely slow speed is 
Option A: Isothermal compression 
Option B: Adiabatic compression 
Option C: Adiabatic expansion 
Option D: All of these 
Explanation: All are extremely slow speed processes

Question No 15 :
Control volume refers to a 
Option A: Specific mass
Option B: Fixed region in the space
Option C: Closed system 
Option D: NONE 
Explanation: Fixed region in the space

Question No 16 : 
The internal energy of a perfect gas depends upon
Option A: Temperature only
Option B: Temperature and pressure 
Option C: Temperature, pressure and specific heats
Option D: NONE
Explanation: Temperature only

Question No 17 :
Joule Thomson coefficient for an ideal gas having equation pV=RT is 
Option A: Zero
Option B: 0.5
Option C: Unity
Option D: Infinite 
Explanation: Zero

Question No 18 :
The temperature of a gas is a measure of 
Option A: Average distance between gas molecules 
Option B: Average kinetic energy of gas molecules
Option C: Average potential energy of gas molecules
Option D: NONE
Explanation: Average kinetic energy of gas molecules

Question No 19 :
A gas, which obeys kinetic theory perfectly is 
Option A: Pure gas
Option B: Real gas
Option C: Perfect gas
Option D: All of these
Explanation: Real gas

Question No 20 : 
The temperature at which, the volume of a gas becomes zero, is called
Option A: Absolute temperature
Option B: Absolute zero temperature
Option C: Absolute scale of temperature
Option D: NONE of these
Explanation: Absolute zero temperature

Question No 21 :
The absolute zero pressure exists 
Option A: At sea level
Option B: At -273 K
Option C: At vacuum condition 
Option D: When the molecular momentum of the system becomes zero 
Explanation: When the molecular momentum of the system becomes zero 

Question No 22 :
Specific heat of gas, Cp = Cv, at
Option A: Absolute zero
Option B: Critical temperature
Option C: Triple point
Option D: All temperatures
Explanation: Absolute zero

Question No 23 : 
The gas constant R is equal to the
Option A: Sum of two specific heats
Option B: Difference of two specific heats
Option C: Product of two specific heats
Option D: Ratio of two specific heat 
Explanation: Difference of two specific heats

Question No 24 : 
Triple point 
Option A: Occurs in a mixture of two or more gases
Option B: In the point, where three phases exist together
Option C: Occurs in sublimation
Option D: None of the above
Explanation: In the point, where three phases exist together

Question No 25 : 
For a pure substance at its triple point, the number of degrees of freedom is 
Option A: 0
Option B: 1
Option C: 2
Option D: None of these
Explanation: Zero 
Consider a system consisting of pure gas, say A. It is, evidently, a one-component, one phase system. The two variable required to be specified will be temperature and pressure. The composition will remain invariable A. The degree of freedom will be 2 if the system will be bivariant. One component system having two phases called mono variant and three phases coexist defines the system completely, therefore, is said to be non-variant or invariant or degree of freedom is zero.  

Question No 26 : 
The efficiency of a Rankine cycle 
Option A: Increases with decreasing temperature of heat rejection
Option B: Decreases with decreasing temperature of heat rejection 
Option C: Decreases with increasing temperature of heat rejection
Option D: None of the above
Explanation: Increase with decreasing temperature and decrease with increasing temperature of heat rejection.

Question No 27 : 
Rankine cycle efficiency for a power plant is 29%. The Carnot cycle efficiency will be
Option A: Less
Option B: More 
Option C: Equal 
Option D: NONE of the above
Explanation: Carnot cycle efficiency is more than the Rankine cycle for the power plant. 

Question No 28 : 
The ideal efficiency of a simple gas turbine cycle depends upon
Option A: Pressure ratio
Option B: Cut-off ratio
Option C: Both A & B
Option D: None of the above
Explanation: Pressure ratio

Question No 29 : 
A system is said to be consisting of a pure substance when 
Option A: It is homogeneous in composition
Option B: It is homogeneous and invariable in chemical aggregation
Option C: It has only one phase
Option D: It has more than one phase
Explanation: It is homogeneous and invariable in chemical aggregation
A pure substance is one which is
Homogeneous in composition 
Homogeneous in chemical aggregation
Invariable in chemical aggregation

Question No 30 :

At its critical point, any substance will 

Option A: Exist all the three phases simultaneously

Option B: Change directly from solid to vapour

Option C: Lose phase distinction between liquid and vapour

Option D: Behave as an ideal gas

Explanation: Lose phase distinction between liquid and vapour

Difference between automatic and manual transmission

Before buying a car there is some tough decision you have to make regarding what you want in your vehicle. There are two types of transmission one is automatic transmission and another one is manual transmission so choose one between these two is important to know the difference between manual and automatic transmission. 

The basic difference between two transmissions is that in manual transmission the driver uses a clutch to change the gears whereas in automatic transmission adjusts the gears automatically based on the engine speed. 

Now let we check some difference between them one by one pointwise below.

Difference : 

• Fuel consumption is more in automatic transmission as compared with manual transmission. 
• A manual transmission gives greater control of the car and auto gearing give lesser control but promises comfort and convenience. 
• A manually transmitted car is cheaper than the same automatically transmitted vehicle.
• Maintenance and repair cost for the automatic transmission is more as compared with manual transmission.  
• In a manual transmission, the gear is located on the floor whereas the location of gear is at the steering or on the floor in the automatic transmission. 
• Manual transmission cars give more mileage than automatic transmission cars. 
• Manual transmission box is lighter than automatic transmission. 
• It is much easier for an automatic transmission to overheat.
• Automatic cars are more often used in sports than manual cars.
• The driver needs to drive with both hand and feet engaged in a manual transmission car where the left foot is totally free in an automatic transmission car. 

What is production system

The production system of an industrial organization is that part which produces products of an organization. The production system has the following characteristics :

• Production is an organized activity, so every production system has an objective. 
• The system transforms various inputs into useful outputs. 
• It does not operate in isolation from the other organization system.

Classification of production system :

1. Job Shop Production 
2. Batch Production 
3. Mass Production 
4. Continuous Production 

Definition of production management

Production is the process which combines and transforms various resources like raw material used in the production system of the industrial organization into finished product or value-added service in a controlled manner as per the policies of the industrial organization.

The set of interrelated management activities, which are involved in manufacturing certain products is called production management. The same concept is extended to services management is called operations management.

Production management deals with converting raw materials into finished products of goods. It brings men, money, machines, materials, methods and markets to satisfy the wants of the people. 

Productivity measurement

Productivity can be measured by two types which are following below :

• By aggregate basis 
• On an individual basis

which is called total and partial measure. 

Total productivity Index / Measure = Total output / Total input 

It can also be measured by Total production of goods and services / Labour + material + capital + Energy + management 

Labour productivity Index / Measure = Output in unit / Man hours worked 

Machine productivity Index / Measure = Total output / Machine hours worked 

Management productivity Index / Measure = Output / Total cost of management 

Land productivity Index / Measure = Total output / Area of land used 

Partial measure can be measure by :

• Output / Labour  
• Output / Capital 
• Output / Materials 
• Output / Energy

Benefits of productivity

For the survival of any industrial organization productivity ratio must be at least 1. If it is more than 1 the organization is in a comfortable position. The ratio of output produced to the input resources utilized in the production.

Benefits derived from higher productivity are as follows :

• Improve profits because productivity helps to cut down cost per unit. 
• Gains from productivity can be transferred to consumers in the form of lower-priced products or better quality products. 
• Paying workers or employees at a higher rate because gains can be shared with them.
• A more productive entrepreneur can have better chances to exploit expert opportunities. 
• Generate more employment opportunity. 
• Overall productivity reflects the efficiency of the production system. 
• More output is produced with the same or less input. 
• The same output is produced with lesser input. 
• More output is produced with more input. 
• The proportional increase in the output is more than the proportional increase in input. 
• It is greatly helpful in achieving overall prosperity and growth of an economy.   

Difference between productivity and production

Production means the process of converting the raw material into the finished product by performing a set of manufacturing operations in a predetermined sequence. Production refers to the absolute output. Thus, if the input increases the output will normally increases in the same proportion. But the productivity remains unchanged. The output increases with the same input of resource or we get the same output with lesser input of the resource, the productivity increases. 

Production means the output in terms of money without any regard to the input of resource while productivity is a human attitude to produces more and more with less and less input of resource.

Now let we summaries the difference between them one by one point wise below.

Differences :

• Production is the act of manufacturing goods for there use or sale while productivity is the rate at which goods are produced.
• Production is actual process of conversion and productivity is the utilization of resources to form goods.  
• Production is measure of produce good while measure of efficiency is called as productivity. 
• Production is process while productivity is measure. 
• Production is number of units actually produced while productivity is ratio of output to input.
• Production is absolute term and productivity is relative term.

Definition of productivity

Productivity is the ratio of financial output in a period of time to the financial input in the same period of time.

Productivity is also called financial efficiency. 

Productivity = Financial efficiency 

= Financial output ( in a period of time ) / Financial input ( in the same period )

In other words, productivity is the quantitative relationship between what we produce and the resource which we used. 

Carter carburetor | Working

Carter carburettor is multiple jets, plain tube type of carburettor with only one adjustment which is for idling or low-speed operation.

Carter carburettor was established in 1909 and founded by William Carter, who started experimenting with automotive carburettors while running a bicycle shop.

Carter carburettor is normally used in Jeeps.

Working of carter carburettor:

A combination of fuel and air is drawn into the nozzle chamber through the jets on side of the nozzle forming a time spray which is carried by the standpipe to the venturi or main air passage, where it is absorbed by incoming air forming mixture on which engine operates.  

Jets on the side of the nozzle come into operation in direct proportion to throttle position. While more and the more throttle opened, the more jets are in operation. At wide-open throttle, all jets are working and the engine is getting maximum supply. 

Low-speed jet assembly supplies fuel to the engine at idle engine speed and up to approximately 20 km/h fuel flowing through a drilled passage connecting low-speed jet chamber with carburettor well. 

At idling, fuel is drawn through a low-speed jet and idling port at the edge of the throttle valve. With the idling screw, the mixture for idle running can be enriched or made leaner as required. 

What is magneto ignition system? | Construction | Working Principle | Advantages

Magneto is one of the special types of ignition systems with its own electric generator to provide the necessary energy for the system.

Construction of the magneto ignition system:

It is mounted on the engine and replaces all the components of the coil ignition system expect the spark plug.

When a magnet is rotated by the engine producing a very high voltage and it does not need a battery as a source of external energy. 

Magneto can be two types :

• Rotating armature type

In this type, the armature consisting of the primary and secondary windings all rotate between the poles of a stationary magnet.

• Rotating magnet type.  

In this type, the magnet revolves and the windings are kept stationary. 

Usually, the third type called polar induction type is also used. In this type, both the magnet and windings remain stationary but the voltage is generated by reversing the flux field with the help of soft iron polar projections is called inductors. 

Working principle of magneto ignition system:

At first, the magnets in flywheel rotate the magneto and magnetic flux of the magnets induces a current in the primary coil by the flywheel. 

A magnetic field develops around the primary coil with current flowing in the primary circuit. This magnetic field also surrounded by the secondary coil.  

The flywheel continues to rotate so the breaker points open and magnetic field produced by the current in the primary winding collapses. 

This collapsing magnetic field flows across the secondary coil which induces a current in the secondary coil. 

There is a winding ratio in the two coils that is 60:1 so the voltage is transformed to the 10000 and 15000 volts needed to fire the spark plug. 

Advantages of magneto ignition system:

• Reliable for medium and high speed. 
• Less maintenance.
• More effective because no battery is used. 

Disadvantages of magneto ignition system:

• Starting problem issue due to low cranking speed at a starting. 
• More expensive compared with the battery ignition system. 
• Possibility of misfire due to leakage because wiring carries very high voltage. 

Applications of magneto ignition system

Magneto ignition system finds applications in the engine where other means of electricity not available, such as chainsaws and lawnmowers because of self-powered characteristics. It also used where other means of electricity also available in the aviation piston engine. The spark intensity increases with the speed of the engine, so it is used in racing cars. Some other applications are following below. 

Application of magneto ignition system : 

• Tractors, oil burners and outboard motors
• Washing machine 
• Trucks and cement mixture trucks
• Used in buses
• Aeroplane engine
• Power units
• Marine and natural gas engines

Advantages and disadvantages of magneto ignition system

Magneto is one of the special types of ignition systems with its own electric generator to provide the necessary energy for the system. The main advantages of a magneto ignition system are it does not require any external source to generate energy. Now you can check out some advantages and disadvantages of the Magento ignition system listed below. 

Advantages of magneto ignition system :

• Reliable for medium and high speed. 
• Less maintenance.
• More effective because no battery is used. 
• Provide better spark at low speed. 
• Occupy less space. 
• Efficiency improves due to high-intensity spark. 

Disadvantages of magneto ignition system :

• Low cranking speed at a starting. 
• Starting is troublesome. 
• More expensive compared with the battery ignition system. 
• Possibility of misfire due to leakage because wiring carries very high voltage. 
• Adjustment of spark timing has determined the effect upon the spark voltage. 

What is engine cooling system

In the engine during the process of converting thermal energy into mechanical energy, the high temperatures are produced in the cylinders of the engine as a result of the combustion process. A large portion of the heat from the gases is transferred to the cylinder head and walls, piston and valves. These parts are damaged and the engine will also be damaged unless heat is carried away so the adequate cooling must be required. 

A cooling system must be provided not only to prevent damage to the vital parts of the engine, but the temperature of these components must be maintained within certain limits in order to obtain maximum performance from the engine. Hence, a cooling system is needed to keep the engine from not getting so hot as to cause problems and yet to permit it to run hot enough to ensure maximum efficiency of the engine. 

The function of the cooling system :

The cooling system keeps the engine from getting not too hot but at the same time not to keep it too cool either. 

Characteristics of an efficient cooling system :

• It should be capable of removing about 30% of the heat generated in the combustion chamber while maintaining the optimum temperature of the engine under all operating conditions of the engine. 
• It should remove heat at a faster rate when the engine is hot. 
• During the starting of the engine, the cooling should be minimum so that the working parts of the engine reach their operating temperatures in a short time. 

Types of the cooling system :

For cooling the engine a cooling medium is required. This can be either air or a liquid. 

According to that two types of the cooling system :

1. Liquid or Indirect cooling system 
2. Air or Direct cooling system 

In the liquid cooling system, there are five methods to cooled the engine. All five are listed below.

1. Direct or non-return system 
2. Thermosyphon system 
3. Forced circulating cooling system 
4. Evaporative cooling system 
5. Pressure cooling system 

In the air cooling system, there are two methods to cooled the engine. These are listed below.

1. Cooling fins 
2. Baffles 

Purpose of cooling system in engine

In the engine during the process of converting thermal energy into mechanical energy, the high temperatures are produced in the cylinders of the engine as a result of the combustion process. A large portion of the heat from the gases is transferred to the cylinder head and walls, piston and valves. These parts are damaged and the engine will also be damaged unless heat is carried away so the adequate cooling must be required. 

A cooling system must be provided not only to prevent damage to the vital parts of the engine, but the temperature of these components must be maintained within certain limits in order to obtain maximum performance from the engine. Hence, a cooling system is needed to keep the engine from not getting so hot as to cause problems and yet to permit it to run hot enough to ensure maximum efficiency of the engine. 

The function of the cooling system :

The cooling system keeps the engine from getting not too hot but at the same time not to keep it too cool either. 

What is capacitive discharge ignition system | Construction | Working | Advantages

The capacitor is used to store the ignition energy and the capacitance and the charging voltage of the capacitor determine the amount of stored energy. An induction coil is used to store the ignition energy in the battery ignition system. 

Construction of the CDI system:

The CDI trigger box includes the capacitor, thyristor power switch, charging device that is used to convert battery voltage to change the voltage of 300 to 500 V by pulse through a voltage transformer and pulse shaping unit and control unit.

Working of CDI system :

This system works by passing an electrical current over a capacitor. This type of ignition builds up a charge very quickly and starts by generating a charge and storing it up before sending it out to the spark plug in order to ignite the engine. 

The power passes through a capacitor and is transferred to an ignition coil that helps to boost the power by acting as a transformer and allowing the energy to pass through it instead of catching.

This system allows the engine to keep running as long as till charge is available in the power source.

Advantages of the CDI system:

• Insensitive to electrical shunts resulting from spark plug fouling.
• This system is suited to an application where insufficient dwell time is available because the capacitor can be fully charged in a very short time. 
• Short transient response.
• A fast voltage rise and shorter spark duration. 

Disadvantages of the CDI system: 

• The spark is strong but short in order to 0.1 to 0.3 ms which leads to ignition failure during lean mixture operating conditions because of fast capacitive discharge.
• This system generates a huge electro-magnetic noise so CDI is rarely used by automobile manufacturers. 

Advantages and disadvantages of capacitive discharge ignition

Capacitor discharge ignition system is an electronic device that stores an electrical charge over a capacitor charge. The capacitor simply charges and discharges within a fraction of time making it possible to create sparks are commonly found on motorbikes and scooters. Let we check some pros and cons of the CDI system in this article. 

Advantages of the CDI system :

• Insensitive to electrical shunts resulting from spark plug fouling.
• It is suited to an application where insufficient dwell time is available because the capacitor can be fully charged in a very short time. 
• Short transient response.
• A fast voltage rise and shorter spark duration. 

Disadvantages of the CDI system : 

• The spark is strong but short in order to 0.1 to 0.3 ms which leads to ignition failure during lean mixture operating conditions because of fast capacitive discharge.
• This system generates a huge electro-magnetic noise so CDI are rarely used by automobile manufacturers. 

Limitation of battery ignition system

In the battery ignition system, the battery is necessary for the ignition so when the battery is discharged it becomes difficult to start the engine. So now let us check out the information on limitations of the battery ignition system to know more about it. 

Limitations of battery ignition system : 

• The current switching capability of the breaker system: As the engine speed increases the primary voltage decreases.
• Dwell period becoming shorter: Time available for a build-up of the current in the primary coil and the stored energy decreases as the engine speed increases. 
• High source impedance: The system is sensitive to side-tracking across the spark plug insulator. 
• Wear: The breaker points are continuously subjected to electrical as well as mechanical wear so frequent maintenance required. 
• As a current increases a rapid reduction in breaker point life and system reliability. 
• Acceptable life for these systems is obtained with a primary current limited to about 4 amperes.