tailieunhanh - Physics exercises_solution: Chapter 29

Bộ tài liệu bài tập tham khảo môn vật lý bậc đại học bằng tiếng anh Chapter 29 | OB NBA and O- NBA cos AOB NBA - cos AONBA 1 - cos s ----- ----------------- At At _ 80 T m m 1 - cos s IS V. a Before OB NBA 200 x 10-5 T 12 x 10-4 m2 x 10-5 T m2 after 0 b i _ AOb _ NBA_ 200 x 10-5 T x 10-3 m2 -4 b S x 10V. 11 At At s x AO NBA Q A w NBA a s ------- ----- IR 1 1R QR NBA Q ------. At At At R b A credit card reader is a search coil. c Data is stored in the charge measured so it is independent of time. From Exercise n_NBA_ 90 T x 10-4 m2 _3 C Cz x 10 C. R Q Q From Exercise _ NBA QR_ x 10-5 C Q Q Q R A 120 x 10-4 m2 a s NdO- NAd B NAd s t x 10 5 T s4 t4 dt dt dtK v 1 s NA T s x 10-4 T s4 t3 V x 10-4 s3 t3. b At t s s V x 10 4 s2 s 3 V I s 6 V x 10-4 A R 600 Q d B d P . f. 2ntïï 2nNAB0 . 2ntV a s ---------- ----NAB A 1 - cos I-----I I ----------0 sinl---I for dt dt _ 0 P T T P T 0 t T zero otherwise. T b s 0 at t 2 c s 2nNAB occurs at t T and t . max T 4 4 d From 0 t y B is getting larger and points in the z direction. This gives a clockwise current looking down the - z axis. From Tt T B is getting smaller but still points in the z direction. This gives a counterclockwise current. a sj d d BA S. A sin60 A sin 60 -d- T e- 5 1 1 indl dt dt nr2 sin 60O T e n m 2 sin 60O T s-1 e V e 0-057 b s s0 V 10 0 10 V V e-0 057 10 ln V10 s 1t t c B is getting weaker so the flux is decreasing. By Lenz s law the induced current must cause an upward magnetic field to oppose the loss of flux. Therefore the induced current must flow counterclockwise as viewed from above. a c 2nr and A ttt2 so A c2 4n B BA B 4n c2 dc dt d dt M B I c 2n At t s c m - s s m H T 1 2n m m s mV b X X I X X x X s X Flux is decreasing so the .