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Bộ tài liệu bài tập tham khảo môn vật lý bậc đại học bằng tiếng anh Chapter 29 | 29.1 OB NBA and O- NBA cos 37.0 AOB NBA - cos 37.0 AONBA 1 - cos 37.0 s ----- ----------------- At At _ 80 1.10 T 0.400 m 0.25 m 1 - cos 37.0 0.0600 s IS 29.5 V. 29.2 a Before OB NBA 200 6.0 x 10-5 T 12 x 10-4 m2 1.44 x 10-5 T m2 after 0 b i _ AOb _ NBA_ 200 6.0 x 10-5 T 1.2 x 10-3 m2 -4 b S 3.6 x 10V. 11 At At 0.040 s x AO NBA Q A w NBA 29.3 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. 29.4 From Exercise 29.3 n_NBA_ 90 2.05 T 2.20 x 10-4 m2 _3 C Cz 2.16 x 10 C. R 6.80 Q 12.0 Q 29.5 From Exercise 29.3 _ NBA QR_ 3.56 x 10-5 C 60.0 Q 45.0 Q Q R A 120 3.20 x 10-4 m2 29.6 a s NdO- NAd B NAd 0.012T s t 3.00 x 10 5 T s4 t4 dt dt dtK v 1 s NA 0.012 T s 1.2 x 10-4 T s4 t3 0.0302 V 3.02 x 10-4 s3 t3. b At t 5.00 s s 0.0302 V 3.02 x 10 4 s2 5.00 s 3 0.0680 V I s 6 V 1.13 x 10-4 A R 600 Q d B d P . f. 2ntïï 2nNAB0 . 2ntV 29.7 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. 29.8 a sj d d BA S. A sin60 A sin 60 -d- 1.4 T e- 5 1 1 indl dt dt nr2 sin 60O 1.4 T 0.057s-1 e n 0.75 m 2 sin 60O 1.4 T 0.057 s-1 e 0.12 V e 0-057 b s s0 0.12 V 10 0 10 0.12 V 0.12 V e-0 057 10 ln V10 -0.057 s 1t t 40.4s 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. 29.9 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 9.0 s c 1.650 m - 9.0 s 0.120 s 0.570 m H 0.500 T 1 2n 0.570 m 0.120 m s 5.44 mV b X X I X X x X s X Flux is decreasing so the .
