Electronics

Chapter 11. A Sling Psychrometer and Relative Humidity:

A Structured-Inquiry Activity

Think About This!

Objectives for the Learner

(Essentials of Inquiry)

How does your comfort level differ on a warm day in

summer from a similarly warm day in autumn?

Sometimes summer temperatures in the mid or upper

eighties in a city, like Washington D.C. along the

Potomac River, will be very uncomfortable, but the

same temperatures in the autumn will feel more

comfortable. What might explain the difference?

Conceptual Theme: To develop a basic understand

ing of the relationship between the temperature and

the amount of moisture that the air can absorb and

how this relationship changes as temperature varies.

Content: Developing a basic understanding of how

a sling psychrometer is used to determine relative

humidity and how to read a chart to determine this

relationship. In addition, the student will establish

a basic understanding of dew point. Further, pro

viding the student additional and basic understand

ings of other factors that constitute the study of

meteorology.

Skills: The focus is using laboratory equipment,

making careful observations, reading a relative

humidity chart, recording data, making conclusions,

and describing and communicating results.

Scientific Habits of Mind: The importance of

careful observations, respect for data, verifying

results, and using equipment safely.

Purpose

To have students construct and use a sling psychro

meter to measure the wet-bulb and dry-bulb tem

peratures, and then use a chart to determine relative

humidity based on the wet-bulb and dry-bulb

readings.

Meteorology Activities for Grades 5-9

47

NP-2006-08-97-LaRC

Materials

2 non-mercury thermometers

15 cm (6 in.) wooden dowel

5 cm (2 in.) wood screw

2 washers

1 cm (0.5 in.) plastic spacer

(such as a section of plastic

drinking straw)

5 cm (2 in.) section of hollow

shoe lace that has been

soaked in water

Safety glasses

Preparation

the washers between the screw head and top ther...