k Ta c6: U -U = 40dB = / g ^ - / g i - = / g ^ = / g ^ = 40 lo ^ g ^ = ^ ^ - * =10000 1 Vgy c/iort cfdp an A Cdu 13: T r o n g chan k h o n g , cac bufc x a diforc s^p xep theo thuf tU bu6c song g i a m dan l a : A t i a h o n g ngoai, a n h sang t i m , t i a tuf ngoai, t i a Rcfn-ghen B t i a Rcfn-ghen, t i a tOf ngoai, a n h sang t i m , t i a h o n g ngoai C t i a h o n g ngoai, a n h sang t i m , t i a Rtfn-ghen, t i a tuf ngoai D a n h sang t i m , t i a h o n g ngoai, t i a tuf ngoai, t i a Rtfn-ghen Giai T r o n g t h a n g song dien tCf, c a c buTc x a di/ac sSp xep theo thuf t i i bi/dfc song g i a m dan l a song v6 t u y e n , t i a h o n g ngoai, a n h sang t r o n g t h a y (tif den t i m ) , t i a tuf ngoai, t i a Rcfn-ghen, t i a gama Vdy chon dap an A Cdu 14: D a t dien a p xoay chieu c6 gia t r i hieu dung k h o n g doi vao h a i dau doan mach gom b i e n t r d R mSc n o i t i e p v i t u d i e n D u n g k h a n g cua t u dien l a 100 Q K h i dieu c h i n h R t h i t a i h a i gia t r i R i v a R2 cong suat tieu t h u cua doan mach nhif B i e t d i e n a p hieu dung giufa hai dau t u d i e n k h i R = R i b k n g h a i I a n d i e n a p h i e u d u n g giOfa h a i dau t u dien k h i R = R2 Cac gia t r i R i v a R2 l a : A R i = Q , R2 = l O O Q B R j = Q , R2 = Q C R i = Q , R = 0 Q D Ri = Q , R = lOOQ Giii Cong suat t i e u t h u cua doan mach luc dau: P = UIcoscp = I^R K h i dieu c h i n h R t h i t a i h a i gia t r i R i v a R2 cong suat t i e u t h u cua doan mach nhiT T a c6: P = ifR, = I j R j (D V i dien a p h i e u dung giffa h a i dau t u dien k h i R = R i b ^ n g h a i I a n dien a p hieu dung giija h a i dau t u dien k h i R = R2 n e n : I i Z c = 2I2ZC => I i = 2I2 Giic Chi ti6t d6 thi T S D H , C D M6n VSt 1( (2) 33