This study source was downloaded by 100000852779192 from CourseHero com on 09 27 2022 16 23 43 GMT 05 00 https www coursehero com file 67124633 4Magnetic Circuits Problemspdf PROBLEMSSECTION 11 3Flux Density1 Using Appendix F ll in the blanks in the followingtable Indicate the units for each quantity 468 MAGNETIC CIRCUITS cid 3 BSI5 cid 4 10 cid 5 4Wb8 cid 4 10 cid 5 4TCGS English cid 3 BSI CGS60 000 maxwells English Area 0 01 m2N turnsI 4 10 4 WbFIG 11 57Problem 3 3 in Ironin 12 b 1 cm6 cmIron2 cm a 0 01 m0 01 mIron0 1 m c FIG 11 58Problem 4 2 Repeat Problem 1 for the following table if area cid 2 2 in 2 3 For the electromagnet of Fig 11 57 a Find the ux density in the core b Sketch the magnetic ux lines and indicate theirdirection c Indicate the north and south poles of the magnet SECTION 11 5Reluctance4 Which section of Fig 11 58 a b or c has thelargest reluctance to the setting up of ux lines throughits longest dimension SECTION 11 6Ohm s Law for Magnetic Circuits5 Find the reluctance of a magnetic circuit if a magnetic ux cid 1 cid 2 4 2 cid 4 10 cid 5 4Wb is established by an impressedmmf of 400 At 6 Repeat Problem 5 for cid 1 cid 2 72 000 maxwells and animpressed mmf of 120 gilberts SECTION 11 7Magnetizing Force7 Find the magnetizing force Hfor Problem 5 in SI units ifthe magnetic circuit is 6 in long 8 If a magnetizing force Hof 600 At m is applied to a mag netic circuit a ux density Bof 1200 cid 4 10 cid 5 4Wb m2isestablished Find the permeability mof a material thatwill produce twice the original ux density for the samemagnetizing force This study source was downloaded by 100000852779192 from CourseHero com on 09 27 2022 16 23 43 GMT 05 00 https www coursehero com file 67124633 4Magnetic Circuits Problemspdf PROBLEMS 469SECTION 11 8Hysteresis9 For the series magnetic circuit of Fig 11 59 determinethe current Inecessary to establish the indicated ux 10 Find the current necessary to establish a ux of cid 1 cid 2 3 cid 4 10 cid 5 4Wb in the series magnetic circuit of Fig 11 60 Area throughout 3 10 3 m2Cast iron 10 10 4 WbMean length 0 2 mN 75 turnsII FIG 11 59Problem 9 Cast ironNISheet steelliron core lsteel core 0 3 mArea throughout 5 cid 2 10 4 m2N 100 turnsFIG 11 60Problem 10 I 1 AN2 30 turnsArea 0 0012 m2lm mean length 0 2 mlmN1I 2 ACast steel FIG 11 61Problem 11 Cast steelSheet steelUniform area throughout 1 in 2lcast steel 5 5 in lsheet steel 0 5 in NIFIG 11 62Problem 12 11 a Find the number of turns N1required to establish a ux cid 1 cid 2 12 cid 4 10 cid 5 4Wb in the magnetic circuit ofFig 11 61 b Find the permeability mof the material 12 a Find the mmf NI required to establish a ux cid 1 cid 2 80 000 lines in the magnetic circuit of Fig 11 62 b Find the permeability of each material 13 For the series magnetic circuit of Fig 11 63 with twoimpressed sources of magnetic pressure determine thecurrent I Each applied mmf establishes a ux pattern inthe clockwise direction Cast steelCast ironIIIArea throughout 0 25 in 2lcast steel 5 5 in lcast iron 2 5 in 0 8 cid 2 10 4 WbN1 20 turnsN2 30 turnsFIG 11 63Problem 13 This study source was downloaded by 100000852779192 from CourseHero com on 09 27 2022 16 23 43 GMT 05 00 https www coursehero com file 67124633 4Magnetic Circuits Problemspdf Powered by TCPDF www tcpdf org SECTION 11 12Air Gaps14 a FindthecurrentIrequiredtoestablisha ux cid 1 cid 2 2 4 cid 4 10 cid 5 4WbinthemagneticcircuitofFig 11 64 b Compare the mmf drop across the air gap to thatacross the rest of the magnetic circuit Discuss yourresults using the value of mfor each material 470 MAGNETIC CIRCUITS 15 The force carried by the plunger of the door chime ofFig 11 65 is determined byf cid 2 cid 3 12 cid 3 NI cid 3 ddfx cid 3 newtons where df dxis the rate of change of ux linking the coilas the core is drawn into the coil The greatest rate ofchange of ux will occur when the core is 1 4to 3 4theway through In this region if cid 1 changes from 0 5 cid 4 10 cid 5 4Wb to 8 cid 4 10 cid 5 4Wb what is the force carried bythe plunger 16 DeterminethecurrentI1requiredtoestablisha uxof cid 1 cid 2 2 cid 4 10 cid 5 4WbinthemagneticcircuitofFig 11 66 0 003 medcbSheet steelaf N 100turnsIArea throughout 2 10 4 m2lab lef 0 05 mlaf lbe 0 02 mlbc ldeIFIG 11 64Problem 14 I 900 mAN 80 turns4 cmfPlungerChimeIFIG 11 65Door chime for Problem 15 0 002 mSheet steel0 3 mI2 0 3 AN2 40 turnsN1 200 turnsI1I1 Area throughout 1 3 10 4 m2FIG 11 66Problem 16 SpringArmatureAir gap 0 2 cmContactsCoilN 200 turnsDiameter of core 0 01 mSolenoidIFIG 11 67Relay for Problem 17 17 a A ux of 0 2 cid 4 10 cid 5 4Wb will establish suf cientattractive force for the armature of the relay of Fig 11 67 to close the contacts Determine the requiredcurrent to establish this ux level if we assume thatthe total mmf drop is across the air gap b The force exerted on the armature is determined bythe equationF newtons cid 2 where Bgis the ux density within the air gap and Ais the common area of the air gap Find the force innewtons exerted when the ux cid 1 speci ed in part a is established B2gA cid 3 mo1 cid 3 2