Constante de Boltzmann

Abstract

Estabeleceu-se, neste trabalho, uma equação barométrica para relacionar as grandezas físicas da baixa atmosfera terrestre: pressão, altitude e temperatura, com a razão entre a constante de Boltzmann e a massa média das moléculas dos gases constituintes. Para uma altitude geopotencial não superior a 33 km e considerando-se a massa média da molécula 4,809 x 10-26 kg, obteve-se um valor médio para a constante de Boltzmann de 1,373 x 10-23 J/K

Analyzing Atmospheric Pressure Variations in Time and Height: a Didactic Proposal Employing a Smartphone Barometer

“…As shown in Table 2, the percentage difference between the values from CETESB and the measurements taken with the smartphone is very small, which attests to the reliability of the device's measurements. Regarding the results, according to the literature, tropical regions have maximum pressure values around 10h00 and around 22h00, therefore within an approximately 12 hours period [32]. These periods and times are observed approximately not only in our measures but also in the data from CETESB (from t2 − t1 ≈ 12 hours and t3 − t2 ≈ 11 hours).…”

“…First, to determine the value of λ, we divide the absolute value of the angular coefficient a = p 1 λ by the linear coefficient b = p 1 in Equation ( 18) to eliminate the dependence of λ on p 1 . To estimate the value of the Boltzmann constant k B , the following parameters were used: local gravity acceleration equal to g = 9.7861 m/s 2 , Avogadro constant N 0 = 6.02 × 10 23 , and average molecular mass of air equal to M = 0.02895 kg/mol, which remains approximately constant throughout the entire altitude range [32]. Under the isothermal hypothesis, the local temperature was also taken using the smartphone and its value was used in Equation ( 13) to estimate the Boltzmann constant.…”

“…Pressure variations with latitude and altitude are also analyzed in [31], using an approximate formula proposed by Laplace. Another work shows the relationship between Halley's law and Boltzmann constant [32].…”