180 Magnetic FieldsP29.62Suppose the input power is120120W V=afI:I~1100A A=.Supposeωπ=FHGIKJFHGIKJ200012200rev minmin60 srad1 revrad s~and the output power is20200rads==τωτbg~101−⋅Nm .Suppose the area is about34cmcm×,orA3−m2.Suppose that the field isB1−T .Then, the number of turns in the coil may be found from ≅NIAB:01131.~NmCsmNsCm2⋅⋅⋅−−NejejgivingN3.*P29.63The sphere is in translational equilibrium, thusfMgs−=sinθ0.(1)The sphere is in rotational equilibrium. If torques are taken about thecenter of the sphere, the magnetic field produces a clockwise torque ofmagnitude µθBsin , and the frictional force a counterclockwise torqueof magnitude fRs, where Ris the radius of the sphere. Thus:Bssin(2)From (1): gs=sin. Substituting this in (2) and canceling out sin,one obtainsµBMgR=.(3)IfsBMgµGGFIG. P29.63Now µπ=NI R2. Thus (3) gives IMgNBR=ππ00898050350 020713...kgm sT mA2afafaf
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This note was uploaded on 12/14/2011 for the course PHY 203 taught by Professor Staff during the Fall '11 term at Indiana State University .