Cdu 27: M o t doan mach A B gom h a i doan mach A M va M B mac noi t i e p Doan m a c h A M c6 dien t r d t h u a n 50 Q mac n o i t i e p vdri cuon cam t h u a n CO tir cam — H , doan mach M B chi c6 t u dien vdri dien 71 dung t h a y ddi diftfc D a t dien ap u = UgCOsl007rt (V) vao h a i dau doan mach A B D i e u c h i n h dien dung cua t u dien den gia t r i C i cho dien ap giCfa h a i dau doan mach A B lech pha ^ so vdri dien ap giufa hai dau doan m a c h A M Gia t r i cua C i bang: A.M«1F 71 B.1^F 71 c -5 71 F D.^F 7t Giai Ta co: Z,=coL = l ^ = 100(Q) 71 = V F + z f = VsO'+lOO' = 50>/5 (Q) Tijf de b a i , t a ve g i a n vectcf nhii h i n h ben Ta c6: AOZ^^R va AOZ^^^Z dong dang v6i nhau, suy r a : ZL _ Z => Zc = ZL =>c = (oZc = 125Q 100 8.10"' 10071.125 Zcw, 71 Vdy chgn dap an A Cdu 28: Theo mSu nguyen tuf Bo, b a n k i n h quy dao K cua electron t r o n g nguyen tuf h i d r o l a ro K h i electron chuyen tii quy dao N ve quy dao L t h i b a n k i n h quy dao g i a m bdrt: A 12ro B 4ro C 9ro D 16ro Giai B a n k i n h d quy dao n l a : rn = n^ro Vdri quy dao K t h i n = 1, quy dao N t h i n = 4, quy dao L t h i n = Chuyen tCf N ve L , ban k i n h quy dao da g i a m bdt: Vdy chgn dap an A _ 68 Giaichitigt