1. The inductance of a magnetic field (shown in Fig. 1) as a function of angular movement is defined by: L(0) = 10+ 0.5 cos(5+0) + 2sin² (30) If the magnetic field is excited by a single winding of 100 turns and I(0) = 10cos(50), find: a. Air-gap reluctance. b. Co-energy for = c. Torque. 2. As shown in Fig. 2, an N-turn electromagnet is to be used to lift a slab of iron of mass M. The surface roughness of the iron is such that when the iron and the electromagnet are in contact, there is an effective air-gap of gmin=0.31mm in each leg. The electromagnet cross-sectional area Ac=32cm² and the 475-turn coil has a resistance of 2.302. Calculate the minimum coil voltage which must be used to lift a slab of mass 12kg against the force of gravity. Neglect the reluctance of the flux path through the iron. Axial length (perpendicular to page)=h Rotor- Fig. 1 N-turn winding Electromagnet, cross-sectional area Ac 8 8 Iron slab, mass M Fig. 2