4th Class Power Engineering Part A Exam Questions with Correct Answers Latest Update
2025/2026
Velocity (m/s) - Answers Change in position / time
Acceleration (m/s^2) - Answers Change in velocity (m/s) / time (s)
Force (Newton) - Answers mass (kg) x acceleration (m/s^2) , any action on a body that tends to
change its size, shape, or its state of rest or motion
Force of Gravity - Answers mass (kg) x 9.81 m/s^2
Pressure (Pa) - Answers Force (N) / area (m^2)
Work (J) - Answers Force (N) x distance (m)
Power - Answers Work done / time , Rate of doing work
Potential Energy (J) - Answers mass x gravity x height , the ability of a body to do work due by
virtue of its position
Kinetic Energy (J) - Answers 1/2 x mass x velocity^2 , The ability of a body to do work due to its
motion
Energy (J) - Answers The capacity of a body to do work
Tonne - Answers 1000 kilograms
Moment of Force (Nm) - Answers Force (N) x Distance (m) , A force, acting on a body at any
distance from a point on that body, will tend to produce rotation around that point
Clockwise Moments - Answers Equal to Counter-clockwise moments
Upward Forces - Answers Equal to Downward forces
Actual Mechanical Advantage (Ma) - Answers Load (N) / Effort (N)
Velocity Ratio (VR) - Answers Distance moved by Effort / Distance moved by Load
Efficiency - Answers Output Work / Input Work
Output Work - Answers Load x Distance moved by load
Input Work - Answers Effort x Distance moved by effort , Equals Output work + Wasted work
Ideal Mechanical Advantage (MA) - Answers Equal to Velocity Ratio (VR)
Load x r - Answers Equal to Effort x R
,VR - Answers Equal to R/r and D/d
Load /Effort - Answers Equal to R/r
Scalar - Answers A physical quantity that has magnitude but no direction
Vector - Answers A quantity that has magnitude and direction
Space Diagram - Answers Illustrates a system of vectors
Co-planar Vectors - Answers Vectors that are all in the same plane
Concurrent Vectors - Answers Vectors whose lines of action meet at one point
Resultant - Answers A vector that represents the sum of two or more vectors
Absolute Pressure - Answers Atmospheric pressure + gauge pressure
Static Friction - Answers A friction force that acts on objects that are not moving. Always
greater than kinetic friction
Kinetic Friction - Answers Friction that opposes motion once the motion has already started.
Not affected by speed of body Always greater than rolling friction.
Rolling Friction - Answers The friction force that acts on rolling objects, Always less than kinetic
friction
Fluid Friction - Answers Friction that occurs as an object moves through a fluid
Force of Friction - Answers Force that resists motion when two materials are in contact.
Proportional to the force that presses the two surfaces together. Not affected by area. Affected
by roughness.
Elasticity - Answers The ability of a material to return to its original shape after being disturbed
Stiffness - Answers Ability of a material to resist a change in shape or size when a load is
applied
Plasticity - Answers Ability of a material to retain its deformed shape when a deforming force is
removed
Ductility - Answers Ability of a material to be stretched and reduced in cross section without
breaking
Toughness - Answers Ability of a material to absorb energy before breaking
Hardness - Answers Ability of a material to resist penetration
Stress - Answers Internal resistance to an external load , Equal to Load (N) / Area (m^2)
,Tensile Stress - Answers Forces that act at opposite ends of a bar and pull away from each
other, creating tension on the bar
Compressive Stress - Answers A stress due to a force pushing together on a body
Shear Stress - Answers Forces on a bar that act parallel to another but are not on the same
plane
Ultimate Stress - Answers The stress at which fracture of the material occurs
Allowable Stress - Answers The greatest stress which a material is capable of developing
without permanent deformation remaining upon the complete release of stress.
Elastic Limit - Answers Maximum stress that a material will withstand without permanent
deformation. Will return to its original size and shape
Factor of Safety - Answers Ultimate Stress / Allowable Stress
Strain - Answers A measure of the deformation produced in a member by a load , Equal to
Change in Length (l) / Original Length (L)
Circumferance - Answers pi x Diameter
Linear Speed - Answers Equal to rev/min x pi D / 60
Four States of Matter - Answers solid, liquid, gas, plasma
Phase - Answers One individual substance in one particular state
Chemical Properties - Answers Only observed when there is a chemical change or reaction ,
Examples are Heat of combustion, Toxicity, Flammability, Chemical Stability
Physical Properties - Answers Characteristics that you can observe without a change in the
composition of matter
Intensive Physical Property - Answers Not dependent on the amount of matter
Extensive Physical Property - Answers Dependent on the amount of matter
Mixture - Answers A combination of two or more substances that are not chemically combined
Homogeneous Mixture - Answers AKA Solution , Only has one set of properties , Possible only
when all the components are in the same physical state , Ex. Flue gas
Heterogenous Mixture - Answers Non-uniform Composition , Substances may or may not be in
the same physical state , Ex. Oil and water emulsion , Sand and water
Matter - Answers Can be described in terms of its states, physical, and chemical properties ,
, State of matter is dependent on its temperature and pressure
Pure Substances - Answers Elements and Compounds
Atomic Number - Answers Represents the number of protons in an atom
First Law of Thermodynamics - Answers The increase in internal energy of a closed system is
equal to the heat supplied to the system minus work done by it (change in work=change in heat)
Second Law of Thermodynamics - Answers Unaided, heat will flow only from a hot substance to
a colder substance
Temperature - Answers A measure of the speed at which the body's molecules vibrate
(higher=higher speed)
Heat - Answers Measure of the sum quantity of internal vibrational energy in a substance
Bimetal Thermometer - Answers Two dissimilar metals are rigidly fixed together and will bend
with temp. change due to their different coefficients of linear expansion
Pyrometer - Answers Measures temp. at the surface of an object
Thermoelectric Pyrometer - Answers Uses a thermocouple to produce an electric voltage which
is proportional to temperature
Optical Pyrometer - Answers Uses the brightness of an object and compares it to a filament to
give the proportional temp.
Infrared Thermometer - Answers Detects infrared energy emissions to measure temp.
Sensible Heat - Answers Heat that can be sensed or detected
Latent Heat - Answers Does not cause a change in temperature when added or removed, but
causes a substance to change state
Specific Heat - Answers The quantity of heat required to raise the temp. of a unit of mass of the
substance by one degree
Quantity or heat absorbed by a substance as it increases in temperature depends on: - Answers
Temperature rise, Mass of the substance, Specific heat of the substance
Thermal Expansion of Plant Equipment - Answers Thermal conditions cause components to
expand or contract. Ex. Length of a rod will increase in length when it is raised in temperature
Heat Transfer - Answers Happens between two bodies if they are different temperatures. Higher
temp. will go to lower temp.
Conduction - Answers Transfer from molecule to molecule within an individual substance or
2025/2026
Velocity (m/s) - Answers Change in position / time
Acceleration (m/s^2) - Answers Change in velocity (m/s) / time (s)
Force (Newton) - Answers mass (kg) x acceleration (m/s^2) , any action on a body that tends to
change its size, shape, or its state of rest or motion
Force of Gravity - Answers mass (kg) x 9.81 m/s^2
Pressure (Pa) - Answers Force (N) / area (m^2)
Work (J) - Answers Force (N) x distance (m)
Power - Answers Work done / time , Rate of doing work
Potential Energy (J) - Answers mass x gravity x height , the ability of a body to do work due by
virtue of its position
Kinetic Energy (J) - Answers 1/2 x mass x velocity^2 , The ability of a body to do work due to its
motion
Energy (J) - Answers The capacity of a body to do work
Tonne - Answers 1000 kilograms
Moment of Force (Nm) - Answers Force (N) x Distance (m) , A force, acting on a body at any
distance from a point on that body, will tend to produce rotation around that point
Clockwise Moments - Answers Equal to Counter-clockwise moments
Upward Forces - Answers Equal to Downward forces
Actual Mechanical Advantage (Ma) - Answers Load (N) / Effort (N)
Velocity Ratio (VR) - Answers Distance moved by Effort / Distance moved by Load
Efficiency - Answers Output Work / Input Work
Output Work - Answers Load x Distance moved by load
Input Work - Answers Effort x Distance moved by effort , Equals Output work + Wasted work
Ideal Mechanical Advantage (MA) - Answers Equal to Velocity Ratio (VR)
Load x r - Answers Equal to Effort x R
,VR - Answers Equal to R/r and D/d
Load /Effort - Answers Equal to R/r
Scalar - Answers A physical quantity that has magnitude but no direction
Vector - Answers A quantity that has magnitude and direction
Space Diagram - Answers Illustrates a system of vectors
Co-planar Vectors - Answers Vectors that are all in the same plane
Concurrent Vectors - Answers Vectors whose lines of action meet at one point
Resultant - Answers A vector that represents the sum of two or more vectors
Absolute Pressure - Answers Atmospheric pressure + gauge pressure
Static Friction - Answers A friction force that acts on objects that are not moving. Always
greater than kinetic friction
Kinetic Friction - Answers Friction that opposes motion once the motion has already started.
Not affected by speed of body Always greater than rolling friction.
Rolling Friction - Answers The friction force that acts on rolling objects, Always less than kinetic
friction
Fluid Friction - Answers Friction that occurs as an object moves through a fluid
Force of Friction - Answers Force that resists motion when two materials are in contact.
Proportional to the force that presses the two surfaces together. Not affected by area. Affected
by roughness.
Elasticity - Answers The ability of a material to return to its original shape after being disturbed
Stiffness - Answers Ability of a material to resist a change in shape or size when a load is
applied
Plasticity - Answers Ability of a material to retain its deformed shape when a deforming force is
removed
Ductility - Answers Ability of a material to be stretched and reduced in cross section without
breaking
Toughness - Answers Ability of a material to absorb energy before breaking
Hardness - Answers Ability of a material to resist penetration
Stress - Answers Internal resistance to an external load , Equal to Load (N) / Area (m^2)
,Tensile Stress - Answers Forces that act at opposite ends of a bar and pull away from each
other, creating tension on the bar
Compressive Stress - Answers A stress due to a force pushing together on a body
Shear Stress - Answers Forces on a bar that act parallel to another but are not on the same
plane
Ultimate Stress - Answers The stress at which fracture of the material occurs
Allowable Stress - Answers The greatest stress which a material is capable of developing
without permanent deformation remaining upon the complete release of stress.
Elastic Limit - Answers Maximum stress that a material will withstand without permanent
deformation. Will return to its original size and shape
Factor of Safety - Answers Ultimate Stress / Allowable Stress
Strain - Answers A measure of the deformation produced in a member by a load , Equal to
Change in Length (l) / Original Length (L)
Circumferance - Answers pi x Diameter
Linear Speed - Answers Equal to rev/min x pi D / 60
Four States of Matter - Answers solid, liquid, gas, plasma
Phase - Answers One individual substance in one particular state
Chemical Properties - Answers Only observed when there is a chemical change or reaction ,
Examples are Heat of combustion, Toxicity, Flammability, Chemical Stability
Physical Properties - Answers Characteristics that you can observe without a change in the
composition of matter
Intensive Physical Property - Answers Not dependent on the amount of matter
Extensive Physical Property - Answers Dependent on the amount of matter
Mixture - Answers A combination of two or more substances that are not chemically combined
Homogeneous Mixture - Answers AKA Solution , Only has one set of properties , Possible only
when all the components are in the same physical state , Ex. Flue gas
Heterogenous Mixture - Answers Non-uniform Composition , Substances may or may not be in
the same physical state , Ex. Oil and water emulsion , Sand and water
Matter - Answers Can be described in terms of its states, physical, and chemical properties ,
, State of matter is dependent on its temperature and pressure
Pure Substances - Answers Elements and Compounds
Atomic Number - Answers Represents the number of protons in an atom
First Law of Thermodynamics - Answers The increase in internal energy of a closed system is
equal to the heat supplied to the system minus work done by it (change in work=change in heat)
Second Law of Thermodynamics - Answers Unaided, heat will flow only from a hot substance to
a colder substance
Temperature - Answers A measure of the speed at which the body's molecules vibrate
(higher=higher speed)
Heat - Answers Measure of the sum quantity of internal vibrational energy in a substance
Bimetal Thermometer - Answers Two dissimilar metals are rigidly fixed together and will bend
with temp. change due to their different coefficients of linear expansion
Pyrometer - Answers Measures temp. at the surface of an object
Thermoelectric Pyrometer - Answers Uses a thermocouple to produce an electric voltage which
is proportional to temperature
Optical Pyrometer - Answers Uses the brightness of an object and compares it to a filament to
give the proportional temp.
Infrared Thermometer - Answers Detects infrared energy emissions to measure temp.
Sensible Heat - Answers Heat that can be sensed or detected
Latent Heat - Answers Does not cause a change in temperature when added or removed, but
causes a substance to change state
Specific Heat - Answers The quantity of heat required to raise the temp. of a unit of mass of the
substance by one degree
Quantity or heat absorbed by a substance as it increases in temperature depends on: - Answers
Temperature rise, Mass of the substance, Specific heat of the substance
Thermal Expansion of Plant Equipment - Answers Thermal conditions cause components to
expand or contract. Ex. Length of a rod will increase in length when it is raised in temperature
Heat Transfer - Answers Happens between two bodies if they are different temperatures. Higher
temp. will go to lower temp.
Conduction - Answers Transfer from molecule to molecule within an individual substance or
