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Đề thi HSG Vật lý THCS (28)

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 O  $4  $4  )  A   9  '4   2 3 1 1 2 2 3 1 D Q = 20(c m + c m ) + Lm D + aB?'-$6: / P%N?1 A SGE  9I A  9'4 4 1 3 Q 862c m= + alO=7c?> 3 4 Q Q=   ⇒  2 1 1 2 2 3 1 D 20(c m + c m ) + Lm D S 1 3 862c m  ⇒  1 1 2 2 3 2 1 1 20(c m + c m ) m = D 862c - L D  ;  GJL+  V   V  V  V   V  V 5 J L  A  N@7c ⇒ r  S  ! "#!$%& ' ()*+,+ A   A  r  Sr A kr / S S 12 12 1 3 U 12 - U - R R ⇒  R A S[JTLF4R /H SHJTL ⇒  12 4 2 A A 2 U I = I + I = + I = R  [e SAJL  ⇒  34 4 4 U R = = I HJ Ω L+  V  V 6 JA VL  C,D%,&)-#"./"0+,12)-. 4E4@,>.,& a26:s A F4:s  N$)d\t(6!+B@E%,@,F@F4 +B@E%,EG+ aT=s A uvs  u →   %H+@IG%JK,GE%J@4LM.NF4$66$W / %H+%JG34 K,GE%J@4LM.NF4$6+  V    V   V  >%,@4LM.NO& aihsq'46:s A F4s  +,!  1 S I // ON  →  1 S S S I S O 6 S O S N S O ′ ′ ′ − = = ′ ′ ′  OI// NF' →  S O S I S O S F' S N S O f ′ ′ ′ = = ′ ′ ′ +  ⇒  S O 6 S O ′ − ′ S S O S O f ′ ′ +   ⇒  f.S O = 6(S O + f) ′ ′ JAL aT= 2 S I // OM Oo(! 2 S F S O S M S O S S S I ′ ′ ′ = = ′ ′ ′   ⇒  S O f S O ′ − = ′ ′ ′ + S O S O 12  ⇒  f.S O = 12(S O - f) ′ ′ JL ,1JALF4JL!wS[JL P ,QR2s!%'44H;; $;>  i6\oN$6(++  xXy_pd\J!3434L$ - eT>s A  A A A S a w E X ′ JzL eT>s   A A A S e w A X ′ JzzL +5   V U U U U e f R A  r r  r A  * /   B r  r / H r H  r B u { | { s s s | A  ,1JzLF4JzzL\-wS[JLF4XqSHJL  xXy06(%FQ=+5 J6")78,9:+ 9#;8<L S JA L a,$4 5#;K@F4$:N?=??`; K@b5# 5c`;KI6!?); F4I?)\d:N$\2'4/+ =>?.8@?+>AB C>)D E"F + 8G2:+>ABH ?.8++#+ ,9 T., amR A/ SAVJTL=R A SEJTLF4R / SGJTL+ ,! 1 12 3 23 R U 6 2 R U 9 3 = = = JAL amR / SAVJTL=R A SAJTLF4R A/ SVJTL+ ,! 2 21 3 13 R U 10 2 R U 5 = = = JL ,1JALF4JL5U A '4?)3d  ⇒ U A SU U  S/U U / SA VU+ amR A SAVJTL+,! 13 1 32 2 U R R 1 U R 3R 3 = = = JzL K;R A/ eR / SR A SAVJTLJzzL ,1JzLF4JzzL!R A/ S/ }VJTLWR / SAA VJTL+ T.,/ amR A/ SAVJTL=R A SEJTLF4R / SGJTL+ ,! 3 12 1 23 R U 6 2 R U 9 3 = = = J/L amR / SAVJTL=R A SAJTLF4R A/ SVJTL+ ,! 3 21 2 13 R U 10 2 R U 5 = = = JHL ,1JALF4JL5U  '4?)3d  ⇒ U  SU U A S/U U / SU+ amR A SAVJTL+,! 13 2 32 1 U R R 1 U R 3R 3 = = = JzzzL K;R A/ eR / SR A SAVJTLJzzzzL ,1JzzzLF4JzzzzL!R A/ S/ }VJTLWR / SAA VJTL+  V  }V  }V A  / U U U A  / A  / U U U A  / . I A1 =0,6A. Sơ đồ 2 ampe kế chỉ I A2 =0,9A. Sơ đồ 3 ampe kế chỉ I A3 =0,5A. Cả ba sơ đồ vôn kế đều chỉ 18V. Tính R 1 , R 2 và điện trở vôn kế. Sơ đồ 1 Sơ đồ 2 Sơ đồ 3 aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa A / U U U A / T U A B T U A U . Bgh[aG 789#'( ĐỀ CHÍNH THỨC : ;<= #  J/ L aih9'4%#&F4'4$N9+  2 AC

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