First law of thermodynamics rate problem

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SUMMARY

The discussion focuses on calculating the rate of increase of energy content in a room containing a 100-W lightbulb, a 110-W TV, a 200-W refrigerator, and a 1000-W iron, all operating simultaneously. The initial temperature of the room is 20 degrees Celsius, and it is assumed that there is no heat transfer through the walls. The relevant equation for energy change is dE/dt = -Q(convection) + W(electrical) - Q(conduction). The user is confused about how to apply the electrical work to find the energy increase and how to determine the average heat transfer coefficient for convection.

PREREQUISITES
  • Understanding of the First Law of Thermodynamics
  • Familiarity with energy transfer concepts, specifically convection and conduction
  • Basic knowledge of electrical power calculations
  • Ability to manipulate equations involving rates of change
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  • Study the First Law of Thermodynamics in detail
  • Learn about heat transfer coefficients and their calculation methods
  • Explore electrical power consumption and its impact on energy content
  • Investigate the principles of convection and conduction in thermodynamics
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This discussion is beneficial for students studying thermodynamics, engineers working with energy systems, and anyone interested in understanding energy transfer in closed systems.

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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.
 

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