# First law of thermodynamics rate problem

## 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 im 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 thats the case, how would i find the average heat transfer coefficiant for Q(conv) since i can cancel out Q(conduction)?

thanks a lot

## Answers and Replies

Borek
Mentor
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.