- #1
Rajo Yajo
- 3
- 0
Homework Statement
The box's measurements are 277*120*195mm.
The lamp's power is 15W.
Trying to figure out how long it will take to heat the box so that it reaches a given temperature.
According to Wikipedia ρair=1,2kg/m3 and cp air=1004J*K-1*kg-1
Homework Equations
ΔU=m*cp*ΔTemperature
E=p*Δt
The Attempt at a Solution
If we suppose that the inside of the box is only air, we will have
vair=0.277*0.120*0.195=0.0064818m3
So, mair=vair*ρair
mair=0.00777816kg
And,
ΔU=mair*cp air*ΔTemperature
We'll have,
ΔU≈7.8ΔTemperature
And if we assume there is no energy loss,
ΔU=E
So
7.8ΔTemperature=15Δt
Thus
Δt=0.52ΔTemperature.
The time I get seems to be too short.
Thanks in advance