Calculate the current required to lift the load for the electromagnet of Example 14.9. Calculate the holding current required to keep the load in place once it has been lifted and is attached to the magnet. Page 860Assume: $N= 700 ; \mu_0=4 \pi \times 10^{-7} ; \mu_r=10^4$ (equal for electromagnet and load); initial distance (air gap) $=0.5 \mathrm{~m}$; magnetic path length of electromagnet $=l_1=0.80$ m ; magnetic path length of movable load $=l_2=0.40 \mathrm{~m}$; gap cross-sectional area $=5 \times 10^{-4} \mathrm{~m}^2 ; m=$ mass of load $=10 \mathrm{~kg} ; g=9.8 \mathrm{~m} / \mathrm{s}^2$.