# Air-Conditioning Questions and Answers – Psychrometric Chart

This set of Air-Conditioning Multiple Choice Questions & Answers (MCQs) focuses on “Psychrometric Chart”.

1. What do vertical and uniformly spaced lines indicate on the psychrometric chart?
a) DPT
b) WBT
c) DBT
d) Specific humidity

Explanation: The psychrometric chart has DBT on the x-axis. So, the vertical and uniformly spaced lines denote dry bulb temperature and spaced by 5°C.

2. Which of the following is represented by curved lines on the psychrometric chart?
a) Specific humidity
b) Relative humidity
c) WBT
d) DPT

Explanation: The psychrometric chart has DBT on the x-axis and specific humidity on the y-axis. The curved line on the grid shows the relative humidity. From 0 to 100 %, these lines are drawn at an interval of 10%.

3. What is represented by inclined straight lines but non-uniformly spaced on the psychrometric chart?
a) Specific humidity
b) Relative humidity
c) WBT
d) DPT

Explanation: The psychrometric chart has DBT on the x-axis and specific humidity on the y-axis. The inclined lines from the saturation curve and on the x-axis denote wet-bulb temperature.

4. What is represented by horizontal lines but non-uniformly spaced on the psychrometric chart?
a) Specific humidity
b) Relative humidity
c) WBT
d) DPT

Explanation: The psychrometric chart has DBT on the x-axis and specific humidity on the y-axis. The horizontal lines from the saturation curve and parallel to the abscissa denote dew point temperature.

5. What is represented by inclined straight lines but uniformly spaced on the psychrometric chart?
a) Enthalpy
b) Relative humidity
c) WBT
d) DPT

Explanation: The psychrometric chart has DBT on the x-axis and specific humidity on the y-axis. The inclined lines from the saturation curve and parallel to the wet-bulb temperature lines denote Enthalpy.

6. What is represented by obliquely inclined straight lines but uniformly spaced on the psychrometric chart?
a) Enthalpy
b) Relative humidity
c) Specific volume
d) DPT

Explanation: The psychrometric chart has DBT on the x-axis and specific humidity on the y-axis. The obliquely inclined lines from the saturation curve and on the dry-bulb temperature lines denote Specific volume.

7. Specific humidity lines are also known as_________
a) moisture content lines
b) relative humidity
c) specific volume
d) moist lines

Explanation: Specific humidity is the moisture present in the air mixture. So, specific humidity denotes moisture content. Hence, these lines are also known as moisture content lines.

8. Relative humidity on saturation curve has value of ________% at various dry bulb temperatures.
a) 0
b) 50
c) 10
d) 100

Explanation: Relative humidity is the ratio of actual mass of water vapor in the given volume of moist air to the mass of water vapor in the same amount of saturated air. So, on the saturation curve, for every dry bulb temperature, the value of relative humidity remains 100%.

9. Enthalpy lines and specific volume lines are the same.
a) False
b) True

Explanation: Though both of the lines representing given properties are inclined straight lines and uniformly spaced, but the slope of both the lines are different. The specific volume lines are obliquely inclined.

10. A psychrometric chart is a graphical representation of various physical properties of dry air.
a) True
b) False

Explanation: Psychrometric chart is a graphical representation of the various thermodynamic properties of moist air. This is used to find out properties of air in the field of air conditioning.

11. Which of the following represents sensible cooling on the psychrometric chart?
a) Horizontal line
b) Vertical line
c) Inclined line
d) Curve

Explanation: Sensible cooling is when DBT decreases. And as per the psychrometric chart, horizontal lines show the change in just DBT and represent sensible cooling.

12. Which of the following represents sensible heating on the psychrometric chart?
a) Horizontal line
b) Vertical line
c) Inclined line
d) Curve

Explanation: Sensible cooling is when DBT rises. And as per the psychrometric chart, horizontal lines show the change in just DBT and represent sensible heating. It is in the opposite direction of sensible cooling.

13. What is the range of DBT on the psychrometric chart usually used?
a) 0 to 30°C
b) 0 to 45°C
c) -6 to 45°C
d) -2 to 45°C

Explanation: Generally, the temperature range of dry bulb temperature lines on the psychrometric chart is from -6 to 45°C. These lines are drawn with a difference of every 5°C of DBT.

14. Which of the following is not correct to fill the blank: The psychrometric chart is normally drawn for standard atmospheric pressure of ________
a) 760 mm of Hg
b) 76 cm of Hg
c) 1.01325 bar
d) 1.01325 torr

Explanation: The psychrometric chart is drawn on the standard values. The standard atmospheric pressure has a value 1.01325 bar. If we convert into other units, then 760 mm of Hg and 76 cm of Hg are also appropriate values of standard pressure, but 1.01325 torr is not. So, this cannot be filled in the blank space.

15. On the Psychrometric chart, the coordinates of any point on it will have abscissa as specific humidity value and ordinate as a dry bulb temperature value.
a) False
b) True

Explanation: The psychrometric chart has DBT and Sp. Humidity on the x-axis and y-axis, respectively. So, any point on the chart will have specific humidity as ordinate and dry bulb temperature as abscissa.

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