A cast steel frame is to be used as the core of an inductor. An 800 turn coil is wound on the centre limb of the frame which has two similar outer limbs in parallel with each other. The frame has the following parameters: Outer limb: c. s.a. of 2000 mm2 and length of 700mm. Centre limb: c. s.a of 4000 mm2 and length of 250 mm. Determine the coil current to set up a flux of 1 mwb if a saw-tooth (an air-gap) of 1 mm is cut in the centre limb. The relative permeability of steel is 1000.

Refrigerant-134a enters the compressor of a refrigerator as superheated vapor at 0.14 mpa and -10°c at a rate of 0.05 ka/s and leaves at 0.8 mpa and 50°c. the refrigerant is cooied in the condenser to 0.72 mpa and 26'c. it is then throttled to 0.15 mpa. sketch the t-s diagram for the system and evaluate: 6) the rate of heat removai from the refrigerated space (kw), it) the power input to the compressor (kw), ii) the isentropic efficiency of the compressor (%), and iv) the cop of the refrigerator.