Lect09 - ! " # ' ( + - ' - $ % # && & )...

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Unformatted text preview: ! " # ' ( + - ' - $ % # && & ) " * , ' . Wa b b a 0 " . / F dl b a + qE dl ' ' + Ua b 05 Wa b b a 1 2 3 45 2 3 562 3 45 qE dl 4 6 4 I A is I, ", w low s flo t f Conductivity high for good conductors. V en tron r u r le c lc e Ohm's Law:n J = E n a io Observables: Observables: tio ct en ire nv d Co :" ote N R= L A L 4 to it e os pp o Analogy to flow of water ( : 8 . " . ' " # " " . 8; . " 9 '' 8 9 # . 8 . 9; 7 .' .' ; ; ' R L A V IR L A A2 4 A1 V2 1V 4 1 L2 2 L1 V2 2V1 < The SAME amount of current I passes through three different resistors. R2 has twice the crosssectional area and the same length as R1, and R3 is three times as long as R1 but has the same cross-sectional area as R1. In which case is the CURRENT DENSITY through the resistor the smallest? A. Case 1 B. Case 2 C. Case 3 J I A J1 J3 J 2J 2 1 A = 8 8 8 8 " ? ? : 6: ( ( ( ( 8 - " ? : ? : ( : : ( 6( - 8 68 38 38 6 38 > Three resistors are connected to a battery with emf V as shown. The resistances of the resistors are all the same, i.e. R1= R2 = R3 = R. .' Compare the current through R2 with the current through R3: B. I2 = I3 C. I2 < I3 A. I2 > I3 8 " 84 8 84 I 23 V R2 R3 @ 8 8 84 8 .' ' 8 " ; ' 8 .' 8 " 84 ' 8 " .' 8 ( ( : :4 : : "# 8 8 84 . "1 8 I 23 V R2 I1 V R1 I1 I 23 R2 R1 R3 2 R3 .' ' 8 " ( 3( ( 3( ( 3( 3 ; 8 1 34 ! ( 3( ( 3( 4 " "# # 8 8 84 8 .' ' 8 " 84 9 / : A :4 : : :4 : :4 B : ' V23 V V23 V2 V3 R2 R3 V2 V3 V2 V3 V 2 : B :4 "# 8 8 84 8 .' ' 8 " 9 : / : : : : : C: : C: C: : : : 3< : C: 8 8 ' ; " 8 84 V 1 V23 R2 R3 V2 V3 V1 2V2 V V23 V2 V3 2V2 8 : 8 ( 8 84 87 8 " 1: 84 4 @: 87 7 : 8% D9 E 1 F 8 D D ': 8 2 38' * "1 " ; 1: ; 8 6 8; 5 2 38 5 6 2 38;5 (8? ( " ' ; 8 ' E 4 8 : 8 ( 8 84 87 8 " 1: 84 4 @: 87 7 : 8% D ; 8 8 8 1 1 295 2/5 ; 8 ' 2 5 ' ; 8 8; 8; Parallel: Can make a loop that contains only those two resistors Series : Every loop with resistor 1 also has resistor 2. 7 8 : 8 ( 8 84 87 8 " 1: 84 4 @: 87 7 : 8% D D 295 8 84 2/5 8 84 2 5 84 2 5 8 2 5 8 " ; " 87 87 ' 8 6 84 6 871 % 87 87 87 ' 28475 " 28 75 " 28 75 " ' ' ' " " " 8 84 84 < 8 : 8 ( 8 84 87 8 " 1: 84 4 @: 87 7 : 28 75 " 8 7 8% ' ; " 84 8 8 8 " 87? 87 8 : 8 : 8 84 8 7 8 : 84 7 84 8 7 295 2/5 2 5 = 8 ( : 8 84 8 7 " 1: 8 84 4 @: 87 7 : D ; 8 1 8% 8 84 87 8 7 8 ' 8 7 47 8 47% 295 8 8 2 38' 47 2/5 8 8 7 47 2 58 8 6 87 38 47 7 2 58 47 = 87 5 2 38 5 6 2 38;5 47 2 345 6 2 3=5 243=5 8 47 > 8 ( : "#$ " 1: 8 "$ @: 87 7 8 8 47 84 "#$ 4 % : " 8% 8 F 8 G 47 ? 8 . 47 6 4 : "#$ F 8 47 * " ( 47 :38 47 @34 =9 ' @ : "#$ 8 ( 47 " 1: 8 "$ @: 87 "#$ 8 84 "#$ 4 7 % : " % 8% 8 : "#$ a ( 47 ( 47 8 "3 8 47 8 b 47 : 47 ( 47 8 47 =G : D 295 : ; : ; 8 2/5 : ; 47 ; % : 2 5: ; : : 2 5: : 2 5: ; =: 8 : 8 47 8 : 84 8 : 8 8 84 87 7 "$ "#$ @: 4 7 "#$ "#$ "#$ % " % & % & " : % " 95 : 84 47 % 47 : 7 7 /5 ( ; ( 7 5/ 96/ 8 47 50 : & 8 " ' F ( 7 * : 7 " 38 3= 9 ' 7 8 : : 8 7 "#$ 8 "$ 8 : 8 8 84 87 "$ "#$ @: 4 7 84 84 87 "#$ "#$ " 95 : 7 % 7 "#$ : /5 ( ( 5/ 96/ 50 "$ "$ % " % & % & " " " & : % 8 87 " ; 8 7 & F # / ; & 0 " : * ( 7: " 8 G & 8 # " 8 H .+ = : " IJ ' 8 8 ; : 84 87 47 : 8 8 84 87 @: 4 7 D 295 (4 :4 (4 % 9 : 47 2/5 (4 : 49 (4 2 5 (4 :4384 79 79 :34 87 = 8 47 : 47 : : 7: (7 9 ' ( 47 = 9 ' D . ( % " ( ( : 38 47 =9 73 9 ( ( 6 (4 $ . %%% 0F# 1 ( ...
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This document was uploaded on 03/08/2012.

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