Magnetic field and transformer
· 1. The electromagnet of Figure has reluctance given by R(x) = 7 x 108(0.002 + x)
H1, where x is the length of the variable gap in meters. The coil has 980 turns and
302 resistance. For an applied voltage of 120 VDC, find:
a. The energy stored in the magnetic field for fr= 0.005 m.
b. The magnetic force for x = 0.005 m.

At steady state, air at 200 kpa, 325 k, and mass flow rate of 0.5 kg/s enters an insulated duct having differing inlet and exit cross-sectional areas. the inlet cross-sectional area is 6 cm2. at the duct exit, the pressure of the air is 100 kpa and the velocity is 250 m/s. neglecting potential energy effects and modeling air as an 1.008 kj/kg k, determine ideal gas with constant cp = (a) the velocity of the air at the inlet, in m/s. (b) the temperature of the air at the exit, in k. (c) the exit cross-sectional area, in cm2