A. Find the current, I, required to establish a flux 0= 2.4x10-4 Wb in the
magnetic circuit of Figure. Here, Area(throughout) = 2x10-4 m², lab = Lef= 0.05 m
laf = lbe = 0.02m, lbc = ldc, and the material is sheet steel.
b. Compare the mmf drop across the air gap to that across the rest of the magnetic
magnetic
circuit. Discuss your results using the value of u for each material.
(NOTICE: find the magnetization curve in page 29 Figure 1.32 in Reference 00
Motor and controlling. The reluctance of sheet steel should be taken into
calculation)

Air is to be cooled in the evaporator section of a refrigerator by passing it over a bank of 0.8-cm-outer-diameter and 0.4-m-long tubes inside which the refrigerant is evaporating at -20°c. air approaches the tube bank in the normal direction at 0°c and 1 atm with a mean velocity of 4 m/s. the tubes are arranged in-line with longitudinal and transverse pitches of sl- st 1.5 cm. there are 30 rows in the flow direction with 15 tubes in each row. determine (a) the refrigeration capacity of this system and (b) pressure drop across the tube bank. evaluate the air properties at an assumed mean temperature of -5°c and 1 atm. is this a good assumption?

An electric kettle is made out of stainless steel, weighs two pounds (when empty) and is equipped with a heating element that consumes 2 kw of electricity. assuming that the water and the kettle are at the same uniform temperature at any moment of time, calculate the shortest possible time to bring 2 quarts of water from room temperature to the onset of boiling

In the winter, in order to keep the classroom steadily at 68 f before 10 pm, heating with an average rate of 42,000 btu/hr is provided. assume the outdoor temperature maintains at 32°f, determine the electrical power (kw) required to (a) operate a reversible heat pump (b) operate a real heat pump with a cop (7) of 4.5 and (c) operate an electrical-resistance heater.