840_Physics ProblemsTechnical Physics

840_Physics ProblemsTechnical Physics - 180 P29.62 Magnetic...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
180 Magnetic Fields P29.62 Suppose the input power is 120 120 W V = af I : I ~1 10 0 A A = . Suppose ω π = F H G I K J F H G I K J 2000 12 200 rev min min 60 s rad 1 rev rad s ~ and the output power is 20 200 r a d s == τω τ bg ~10 1 Nm . Suppose the area is about 34 cm cm × ,o r A 3 m 2 . Suppose that the field is B 1 T . Then, the number of turns in the coil may be found from NIAB : 01 1 31 .~ Nm Cs m NsCm 2 ⋅⋅ −− N ej e j giving N 3 . *P29.63 The sphere is in translational equilibrium, thus fM g s −= sin θ 0. (1) The sphere is in rotational equilibrium. If torques are taken about the center of the sphere, the magnetic field produces a clockwise torque of magnitude µθ B sin , and the frictional force a counterclockwise torque of magnitude fR s , where R is the radius of the sphere. Thus: B s sin (2) From (1): g s = sin . Substituting this in (2) and canceling out sin , one obtains µ BM g R = . (3) I f s B Mg µ G G FIG. P29.63 Now µπ = NI R 2 . Thus (3) gives I Mg NBR = ππ 008 980 503 5 0 02 0713 .. . kg m s T m A 2 a fa fa f
Background image of page 1
This is the end of the preview. Sign up to access the rest of the document.

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 .

Ask a homework question - tutors are online