Please answer part B. A class of 10 students taking an exam has a power output p
ID: 1469432 • Letter: P
Question
Please answer part B.
A class of 10 students taking an exam has a power output per student of about 200 W. Assume that the initial temperature of the room is 20°C and that its dimensions are 6.0 m by 15.0 m by 3.0 m. What is the temperature of the room at the end of 1.0 h if all the energy remains in the air in the room and none is added by an outside source? The specific heat of air is 837 J/kg • °C, and its density is about 1.3 x 10–3 g/cm3.
Part B) how long would the students have to sit in the exam room for the temperature to rise from 20 degrees Celsius to 100 degrees Celsius, assuming they can maintain the same power output?
Explanation / Answer
Q = m*Cair*dT
Q = D*V*Cair*dT
but heat Q = P*t
therefore
n*P*t = D*V*Cair*dT
density = D = 1.3*10^-3 = 1.3*10^-3*10^3 kg /m^3 = 1.3 kg/m^3
10*200*t = 1.3*6*15*3*837*(100-20)
time = t = 11751.48 s
t = 3.26 h