Problem : Imagine your windows are stuck shut in your room as you are leaving fo

Question

Problem: Imagine your windows are stuck shut in your room as you are leaving for your morning classes and you don’t want it to be hot in your room when you return from class in the afternoon, so you turn on a fan.  Will your room be hotter or cooler than it would have been without the fan upon your return?  Use an energy balance-based analysis to make a determination. (hint:  assume the power used by the fan is converted into two quantities:  work associated with rotating the fan blades, and heat for dissipation of power by electrical resistance within the motor)

Explanation / Answer

based on enery balance analysis,

the room becomes warmer when he returns the room because as there is no ventilation provided (windows shut), electrical work is done here through the wires into the room (that is energy is added to the room in the form of heat dissipation of power).

thus through convection heat is transfered through out the room.

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