A 15cm x 20cm printed circuit board is to be cooled by natural convection at room temperature of 20oC. The PCB is dissipating heat at 8W f power in steady operation, determine average temperature of the hot surface of the board when (a) the board is vertical, (b) horizontal with hot surface facing up, and (c) horizontal with hot surface facing down. Emissivity of the board surface is 0.8/

What type of light does this light bulb produce most (i. e. at what wavelength does the spectrum have maximum intensity)?

When the magnetic domains in a material can be aligned, but eventually drift out of alignment, the material is

4r-134a enters the condenser of a residential heat pump at 800 kpa and 50°c at a rate of 0.022 kg/s and leaves at 750 kpa subcooled by 3°c. the refrigerant enters the compressor at 200 kpa superheated by 4°c determine (a) the isentropic efficiency of the compressor, (b) the rate of heat supplied to the heated room, and (c) the cop of the heat pump. also, determine (d) the cop and rate of heat supplied to the heated room if this heat pump operated on the ideal vapor-compression cycle between the pressure limits of 200 and 800 kpa. (0.757, 4.37 kw, 5.12, 6.18, 3.91 kw)