4th Class Power Engineering Practice Questions competency test 1 to 40

Question 1

Psychometry is a science that studies:B
A) the behaviour of human beings.
B) the behaviour or mixtures of air and watervapor.
C) the prediction of the future.
D) measurement of the molecular composition of air.
E) the mental state of people.


Question 2

Comfort air conditioning, besides controlling air temperature, also involves
the control of the:C
1. moisture content of air
2. density of air
3. cleanliness of air
4. composition of air
A) 1 and 2 ONLY
B) 2 and 3 ONLY
C) 1 and 3 ONLY
D) 2, 3 and 4 ONLY
E) 1, 3 and 4 ONLY


Question 3

Air found in nature always:B
1. is pure and dry
2. has moisture in it
3. contains 21% nitrogen in volume
4. has minute amounts of carbon dioxide, hydrogen
A) 1, 3, and 4 ONLY
B) 2, 3, and 4 ONLY
C) 2 and 3 ONLY
D) 1 and 4 ONLY
E) 2 and 4 ONLY


Question 4

Humidity is defined as:C
A) the maximum amount of water vapour air can hold.
B) the mass of water vapour per unit volume of air.
C) the presence of moisture in the air.
D) the relative amount of moisture in the air at 30 ?C.
E) the quantity of moisture in liquid phase in the air per unit mass of gas


Question 5

Specific humidity is measured:A
A) in kg of water vapour per kg of dry air.
B) in cubic metres of water vapour per cubic metre of dry air.
C) as percentage of water vapour in the air.
D) as mass of water vapour in dry air.
E) as mass of water per unit volume of air.


Question 6

Absolute humidity is defined as:B
A) the maximum amount of water vapour air can hold.
B) the actual mass of moisture per unit mass of dry air.
C) the water vapour in the ambient air.
D) the relative volume of moisture in the air.
E) the quantity of moisture in liquid phase in the air.


Question 7

Relative humidity is defined as:A
A) the ratio of the actual mass of water vapour in a given amount of air
compared to the maximum mass the air can hold at that temperature.
B) the mass of water vapour in the air at a specific dry bulb temperature.
C) the mass of water vapour in the air at a specific wet bulb temperature.
D) the ratio of mass of dry air to the mass of wet air.
E) the ratio of the mass of liquid water in the air to the mass of air.


Question 8
Dalton's Law of partial pressures states that:B
A) for every given pressure there is an opposite pressure.
B) in a mixture of two or more gases each will exert a partial pressure
which is equal to the
pressure that it would exert if it filled that space alone.
C) the partial pressure exerted by two or more gases on the wall of the
containing vessel
is a constant R.
D) the sum of the mass of air and water vapour in a vessel is equal to the
total pressure.
E) water vapour is not included when calculating total air pressure.


Question 9

Dew point temperature is the temperature at which:C
A) dew starts to evaporate in the morning.
B) dew disappears in the morning.
C) water vapour in the air begins to condense.
D) the air reaches the freezing point.
E) water reaches its freezing point.


Question 10

If 50 grams/kg of dry air at 25 ?C represents saturated air, 15 grams of
water vapour/kg of dry air at the same temperature indicates a relative
humidity of:C
A) 3.3%
B) 15%
C) 30%
D) 35%
E) 50%


Question 11

Wet bulb temperature reading:C
A) is determined only when it is raining.
B) is determined when the thermometer is immersed in water.
C) is lower than the dry bulb temperature reading.
D) is the same number as the relative humidity in the air
E) is higher than the dry bulb reading due to the effect of a wetted wick on
the thermometer.


Question 12

The difference between the dry bulb temperature and the wet bulb temperature
is termed:B
A) the dry bulb depression.
B) the wet bulb depression.
C) the humidity depression.
D) the correction factor.
E) the wet/dry factor.


Question 13

Relative humidity is determined using a:D
A) manometer
B) humidistat
C) hydrometer
D) psychrometer
E) dry bulb hydrometer


Question 14

Given a dry bulb temperature reading of 28?C and a wet bulb temperature
reading of 22?C, the relative humidity is: G
A) 50%
B) 54%
C) 58%
D) 60%
E) 62%


Question 15

In air handling equipment calculations, "standard air" refers to dry air
at::C
A) 21?C and in excess of 105.3 kPa.
B) 21?C and 105.3 kPa.
C) 21?C and 101.3 kPa.
D) 25?C and 101.3 kPa.
E) 25?C and less than 101.3 kPa.


Question 16

The unit of measurement for specific volume of air is:C
A) kJ/kg of dry air.
B) kg/kg of dry air.
C) cubic meters/kg of dry air.
D) kg/cubic metre of dry air.
E) cubic metres/cubic metre of dry air.


Question 17

The volume of standard air is _________ cu m/kg of dry air.D
A) 0.533
B) 0.633
C) 0.733
D) 0.833
E) 0.933


Question 18

Enthalpy of an air mixture measures the :D
A) moisture content of the air mixture.
B) sensible heat content of the dry air.
C) latent heat content of the moist air.
D) total heat content of the air mixture.
E) sensible heat content of the air mixture.


Question 19

The heat content of dry air is calculated using the base as:A
A) 0 °C
B) 4 °C
C) 21 °C
D) 25 °C
E) 100 °C


Question 20
The heat content of an air mixture is called:A
A) enthalpy
B) latent heat
C) specific temperature.
D) allotropic content
E) entropy

Question 21

The psychometric chart:B
1. graphically illustrates various properties of air-vapour mixtures.
2. can be used to check the performance of an air conditioning system.
3. is available for different fluids and refrigerants
4. simplifies calculations involving air
A) 1, 2 and 3 ONLY
B) 1, 2 and 4 ONLY
C) 2, 3, and 4 ONLY
D) 1, 2, 3, and 4 ONLY


Question 22

On the psychometric chart, the vertical lines are used to indicate:B
A) wet bulb temperature.
B) dry bulb temperature.
C) specific humidity.
D) enthalph.
E) specific volume


Question 23

On the psychometric chart, lines that originate on the left side, along the
saturation line, and slope downward to the right are used to indicate:E
A) wet bulb temperature and relative humidity.
B) enthalpy and specific humidity
C) dew point temperature and specific humidity
D) wet bulb temperature and specific gravity.
E) wet bulb temperature and specific volume.


Question 24
On the psychometric chart, the horizontal lines that originate on the left
side along the saturation line are used to indicate:D
A) wet bulb temperature and relative humidity
B) enthalpy and specific humidity
C) dew point temperature and specific humidity
D) wet bulb temperature and specific humidity
E) dew point temperature and relative humidity


Question 25

The property of air that cannot be determined using a psychometric chart is
the:B
A) dew point temperature
B) partial pressure
C) specific humidity
D) enthalpy
E) specific volume


Question 26

On the psychometric chart, the intersection between a line running
vertically upwards from the dry bulb scale and a line running diagonally
downwards from the wet bulb scale is defined as the:C
A) dew point temperature
B) partial pressure
C) reference point
D) specific volume
E) relative humidity


Question 27

In a process of simply raising the temperature of air without changing its
moisture content, the heat added is:A
A) sensible heat only
B) latent heat only
C) sensible heat and latent heat
D) sensible heat and superheat
E) latent heat and superheat


Question 28

If air is cooled from 38°C dry bulb temperature to 15°C dry bulb temperature
without changing the moisture content, the wet bulb temperature of the air
will:B
A) stay the same
B) increase
C) decrease
D) increase, depending on the wind velocity
E) decrease, depending on the humidity


Question 29

When air is cooled without changing the moisture content, heat added or
removed is called __________ heat.D
A) evaporation
B) condensation
C) latent
D) sensible
E) fusion


Question 30

Sensible heating or cooling, if plotted on the psychrometric chart, is a:C
A) straight vertical line.
B) straight line sloped up from left to right.
C) straight horizontal line.
D) straight line sloped up from the right to the left.
E) curved line sloped up from the left to right.


Question 31

Sensible heating of air will result in a decrease in:B
A) dew point temperature.
B) relative humidity.
C) specific humidity
D) dry bulb temperature.
E) wet bulb temperature.


Question 32

In psychometry, addition of latent heat only to air will cause: C
A) an increase in the dry bulb temperature.
B) a decrease in the dry bulb temperature.
C) an increase in the specific humidity.
D) a decrease in the specific volume.
E) a decrease in the dew point temperature.


Question 33

The single piece of equipment that can be used to cool and humidify the air
is:B
A) an evaporator
B) an air washer
C) a cooling coil
D) a de-humidifier
E) a DX coil


Question 34

Cooling and humidification is also referred to as:D
A) latent cooling
B) sensible cooling
C) solar evaporation
D) evaporative cooling
E) spray humidification


Question 35

Spray water used in cooling and humidification of air: A
A) does not require additional heating or cooling.
B) must be cooled before use.
C) must be heated before use.
D) must have a small amount of sodium chloride added.
E) must have a small amount of calcium chloride added.


Question 36

Which of the following statements about cooling and dehumidification is
FALSE?D
A) Air washers are used to dehumidify air.
B) Air leaving the washer will be close to 100% relative humidity.
C) The spray water carries off the latent heat of condensation of the water
vapour in the air.
D) Dry bulb temperature is increased.
E) Dew point temperature is lowered.


Question 37

In an air conditioning system, ventilation: C
1. provides fresh air to flush out some of the stale air.
2. reduces the load on the air conditioning system.
3. minimizes air infiltration into the building.
4. maintains the building at a positive pressure.
5. provides make-up for exhaust air.
A) 1, 2 and 3 ONLY
B) 2, 3 and 4 ONLY
C) 1, 3, 4, and 5 ONLY
D) 2, 3, 4 and 5 ONLY
E) 1, 2, 3, 4, and 5


Question 38

A measure of comfort involving the combined effects of dry-bulb temperature,
relative humidity and air movement is referred to as: C
A) relative comfort zone.
B) effective comfort zone.
C) effective temperature.
D) specific temperature.
E) relative temperature zone.


Question 39

The comfort of human beings is affected by the atmospheric conditions
surrounding them. Which of the following is NOT an atmospheric condition: C
A) temperature
B) relative humidity
C) saturation temperature
D) air cleanliness
E) air movement


Question 40

During summer, an air conditioned space should ideally have a relative
humidity of 50% and a dry-bulb temperature of: D
A) 21.4°C.
B) 22.4°C.
C) 23.4°C.
D) 24.4°C.
E) 25.5°C.