First law of thermodynamics rate problem

AI Thread Summary
The problem involves calculating the rate of energy increase in a room containing several electrical devices, given that no heat is lost through the walls. The total power consumption of the devices is 1410 W (100 W lightbulb, 110 W TV, 200 W refrigerator, and 1000 W iron). The first law of thermodynamics is applied, considering electrical work and convection heat transfer. The discussion highlights confusion regarding the relationship between electrical work and the rate of energy increase, as well as the calculation of heat transfer coefficients. The key takeaway is that with no heat loss, the energy content of the room increases at the rate of the total electrical power consumed.
tron_2.0
Messages
29
Reaction score
0

Homework Statement


consider a room that is initially at the outdoor temperature of 20 degrees C. The room contains a 100-W lightbulb, a 110-W TV set, a 200-W refrigerator, and a 1000-W iron. Assuming no heat transfer through the walls, determine the rate of increase of the energy content of the room when all of these electric devices are on.


Homework Equations


dE/dt (of the control mass)= -Q(convection)+W(electrical)-Q(conduction)
W(electrical)=Q(convection)?

The Attempt at a Solution


I tried to take into account that the electrical work is given, but I am unsure on how this correlates to the rate of increase of energy. am i solving the first equation i wrote for dE/dt? and if that's the case, how would i find the average heat transfer coefficiant for Q(conv) since i can cancel out Q(conduction)?

thanks a lot
 
Physics news on Phys.org
You are told to assume no heat is lost.

Honestly, I have no idea what to make out of your analysis of the problem, it seems to be completely off.
 
Thread 'Confusion regarding a chemical kinetics problem'

Thread 'Confusion regarding a chemical kinetics problem'

TL;DR Summary: cannot find out error in solution proposed. [![question with rate laws][1]][1] Now the rate law for the reaction (i.e reaction rate) can be written as: $$ R= k[N_2O_5] $$ my main question is, WHAT is this reaction equal to? what I mean here is, whether $$k[N_2O_5]= -d[N_2O_5]/dt$$ or is it $$k[N_2O_5]= -1/2 \frac{d}{dt} [N_2O_5] $$ ? The latter seems to be more apt, as the reaction rate must be -1/2 (disappearance rate of N2O5), which adheres to the stoichiometry of the...
View full post »

Thread 'Prove that evolution is constant (Provide at least two arguments to support your position)'

I don't get how to argue it. i can prove: evolution is the ability to adapt, whether it's progression or regression from some point of view, so if evolution is not constant then animal generations couldn`t stay alive for a big amount of time because when climate is changing this generations die. but they dont. so evolution is constant. but its not an argument, right? how to fing arguments when i only prove it.. analytically, i guess it called that (this is indirectly related to biology, im...
View full post »

Similar threads

Chemistry How to understand the energy involved in mass transfer into an open system?
Replies
0
Views
1K
Chemistry How to derive 2nd law extremum principles for U, A, G, and H?
Replies
1
Views
2K
Chemistry Calculation of thermodynamic variables for irreversible adiabatic process of ideal gas
Replies
9
Views
2K
Chemistry Show that book levitation by absorption of heat violates 2nd law
Replies
13
Views
2K
I Application of the first law of thermodynamics
Replies
46
Views
6K
Chemistry Entropy in isolated composite system for irreversible process
Replies
3
Views
2K
First law of thermodynamics and the work done on a system
Replies
13
Views
2K
Chemistry: First principle of thermodynamics
Replies
4
Views
2K
Why is delta-H equal to q at constant pressure?
Replies
11
Views
3K
Chemistry How to explain the difference between recompression of ideal gas reversibly and irreversibly after initial irreversible expansion?
Replies
5
Views
2K

Hot Threads

Recent Insights

Back
Top