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投稿者 スレッド
webadm
投稿日時: 2007-8-30 20:03
Webmaster
登録日: 2004-11-7
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投稿: 3068
問題31:ブリッジの逆接続
問題31は問題30のおまけみたいなもの。

同じブリッジ回路で剣流計と電池を取り替えて接続した場合に、剣流計に流れる電流の逆数の差を求めるもの。

出題の意図がいまいちわからない。電流の逆数という概念も今まで登場してこなかっただけに何を意味するのか不明。電流値に反比例する尺度ってなんだ、電流の流れ難さ? 抵抗の逆数はコンダクタンスというのは出てきたけど。電流の逆数に電圧をかければ抵抗値になるという関係はある。

抵抗を2つだけ動かして剣流計と電池を入れ替えたのと同じ回路にしなさいという、マッチ棒クイズみたいにも見える。

実際に著者の解答はそうしたものだった。これも2つの回路の間の間違い探しみたいな、パターンの発見というか直感力を試すもので、回路解析とはとどのつまりそういうことだと言いたいのかもしれない。

まじめに解くと、問題30の回路で剣流計と電池を交換した回路図を描いて、同じように剣流計に流れる電流の式を求めて、2つの回路のそれぞれの剣流計に流れる電流の逆数の差を求めれば良いことになる。

元の回路の剣流計に流れる電流Igは

Ig = (R2*R3 - R1*R4)*E/(Rg*(R1 + R2)*(R3 + R4) + R1*R2*(R3 + R4) + R3*R4*(R1 + R2))

同じ回路で剣流計と電池を取り替えた時に剣流計に流れる電流Ig'は、以下の方程式を解くことによって得られる。

E = I1*R1 + (I1 - Ig')*R3
E = (I - I1)*R2 + (I - I1 + Ig')*R4
E = I1*R1 + Ig'*Rg + (I - I1 + Ig')*R4

これを例によってMaximaを使って解くと

(%i1) e1: E=I1*R1 + (I1 - Ig)*R3;
(%o1) E=(I1-Ig)*R3+I1*R1
(%i2) e2: E=(I - I1)*R2 + (I-I1+Ig)*R4;
(%o2) E=(-I1+I+Ig)*R4+(I-I1)*R2
(%i3) e3: E=I1*R1 + Ig*Rg + (I-I1+Ig)*R4;
(%o3) E=(-I1+I+Ig)*R4+I1*R1+Ig*Rg
(%i4) solve([e1,e2,e3],[I,I1,Ig]);
(%o4) [[I=(E*((R2+Rg)*R4+Rg*R2)+E*R1*(R4+Rg)+(E*(R2+Rg)+E*R1)*R3)/(R3*(R1*(R4+R2)+(R2+Rg)*R4+Rg*R2)+R1*((R2+Rg)*R4+Rg*R2)),I1=
(E*((R2+Rg)*R4+Rg*R2)+E*R2*R3)/(R3*(R1*(R4+R2)+(R2+Rg)*R4+Rg*R2)+R1*((R2+Rg)*R4+Rg*R2)),Ig=
(E*R2*R3-E*R1*R4)/(R3*(R1*(R4+R2)+(R2+Rg)*R4+Rg*R2)+R1*((R2+Rg)*R4+Rg*R2))]]

整理すると

Ig' = (R2*R3 - R1*R4)*E/(R3*R1*R4 + R3*R1*R2 + R3*R4*R2 + R3*R4*Rg R3*R2*Rg + R1*R4*R2 + R1*R4*Rg + R1*R2*Rg)
= (R2*R3 - R1*R4)*E/(Rg*(R3*R4 + R3*R2 + R1*R4 + R1*R2) + R1*R2*(R3 + R4) + R3*R4*(R1 + R2))
= (R2*R3 - R1*R4)*E/(Rg*(R1 + R3)*(R2 + R4) + R1*R2*(R3 + R4) + R3*R4*(R1 + R2))

Rgに関係する項以外は以前と同じ。

従って

1/Ig - 1/Ig' =
(Rg*(R1 + R2)*(R3 + R4) + R1*R2*(R3 + R4) + R3*R4*(R1 + R2))/(R2*R3 - R1*R4)*E - (Rg*(R1 + R3)*(R2 + R4) + R1*R2*(R3 + R4) + R3*R4*(R1 + R2))/(R2*R3 - R1*R4)*E
=(Rg*(R1 + R2)*(R3 + R4) - Rg(R1 + R3)*(R2 + R4))/(R2*R3 - R1*R4)*E
=(Rg*(R1*R3 + R2*R3 + R1*R4 + R2*R4 - R1*R2 - R3*R2 - R1*R4 - R3*R4))/(R2*R3 - R1*R4)*E
=(Rg*(R1*R3 + R2*R4 - R1*R2 - R3*R4))/(R2*R3 - R1*R4)*E
=(Rg*(R3 - R2)*(R1 - R4))/(R2*R3 - R1*R4)*E

として同じ結果が得られた。

これと著者の解き方以外にも、問題30で求めた剣流計に流れる電流の式をRg=0,R2=3*R1,R3=3*R4にして書き換えることによっても同様の結果が得られるはず。

剣流計以外の電流の式は二次式とか出て来て恐ろしいことになっているが因数分解すればもっとシンプルな式になることは想像がつく。

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題名 投稿者 日時
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       分圧回路の実験 webadm 2007-2-3 1:35
         別の測定器でやってみた webadm 2007-2-3 13:47
           さらなる考察 webadm 2007-2-3 22:41
             そのほか考慮すべき点 webadm 2007-2-15 5:09
     直流回路の演習問題を見て webadm 2007-2-4 5:12
       初等の数学をすっかり忘れている webadm 2007-2-4 11:43
         なんとか出来た webadm 2007-2-4 12:33
     格子状抵抗ネットワークの意味 webadm 2007-2-4 21:13
       インピーダンスの思い出 webadm 2007-2-11 23:25
         dBとか webadm 2007-2-12 5:14
           Re: dBとか webadm 2007-4-2 5:29
             Boonton Radio CorpのThe Notebook webadm 2007-4-10 12:53
       早くも躓く webadm 2007-2-13 11:02
         まだ11ページしか進んでいない webadm 2007-2-15 3:51
           実学と理論 webadm 2007-2-22 6:56
             網目電流法の演習 webadm 2007-2-24 22:47
               やっと解けた webadm 2007-2-28 21:21
                 黒板かホワイトボードが欲しい webadm 2007-3-2 0:13
                   やっとp12問題9 webadm 2007-3-3 3:53
                     問題9完了 webadm 2007-3-4 3:44
                       問題10:正三角錐型ワイヤーフレーム webadm 2007-3-4 13:05
                         問題11:3x3格子状ワイヤーネットワーク webadm 2007-3-6 19:36
                           問題12:正立方体格子ワイヤー網 webadm 2007-3-8 10:37
                             問題14:3つのΔ接続ワイヤー網 webadm 2007-3-9 5:54
                               問題15:アッテネーターぽい回路 webadm 2007-3-23 11:59
                                 問題16:Δ接続・Y接続 webadm 2007-3-24 12:40
                                   問題17、18、19 webadm 2007-3-24 22:55
                                     問題20,21:枝電流法と網目電流法を誤解していた疑い webadm 2007-3-25 12:57
                                       問題22:電流計 webadm 2007-3-26 11:39
                                         問題23:電流計と電圧計 webadm 2007-3-26 12:03
                                           問題24:T型アッテネーター webadm 2007-3-27 11:19
                                             問題25:パイ型アッテネーター webadm 2007-3-30 19:49
                                               Re: 問題25:パイ型アッテネーター webadm 2007-4-12 11:16
                                                 Re: 問題25:パイ型アッテネーター webadm 2007-4-12 21:44
                                               問題26:検流計の内部抵抗を求める webadm 2007-5-4 13:34
                                                 問題27:抵抗計 webadm 2007-5-4 15:28
                                                   問題28:アッテネーター webadm 2007-8-18 9:57
                                                     問題29:ボリューム(アッテネーター) webadm 2007-8-22 18:26
                                                       問題30:ブリッジ回路解析 webadm 2007-8-26 12:05
                                                         Re: 問題30:ブリッジ回路解析 webadm 2007-8-26 22:25
                                                           Maxima超便利 webadm 2007-8-27 1:16
                                                             数式処理システムの問題点 webadm 2007-8-28 10:19
                                                             » 問題31:ブリッジの逆接続 webadm 2007-8-30 20:03
                                                                 問題32:剣流計の内部抵抗が0のブリッジ回路 webadm 2007-8-30 20:21
                                                                   問題33:平衡ブリッジによる抵抗測定 webadm 2007-9-1 11:16
                                                                     問題34:ひねったブリッジ回路 webadm 2007-9-5 14:27
                                                                       問題35:内部抵抗がない剣流計を流れる電流 webadm 2007-9-6 8:42
                                                                         問題36:バイパスされたT型アッテネーター webadm 2007-9-15 3:54
                                                                           問題37:Kelvinのダブルブリッジ webadm 2007-9-15 18:10
                                                                             問題38:地絡距離測定 webadm 2007-9-15 19:36
                                                                               問題39:キャパシタの並列接続 webadm 2007-9-21 19:33
                                                                                 問題40:キャパシタの直列接続 webadm 2007-9-21 19:53
                                                                                   問題41:コンデンサの直列接続計算 webadm 2007-9-22 3:54
                                                                                     問題42:コンデンサの直・並列組み合わせ回路計算 webadm 2007-9-22 19:26
                                                                                       問題43:コンデンサのY接続 webadm 2007-9-23 3:31
                                                                                         問題44:コンデンサーのラダー回路 webadm 2007-9-23 4:42
                                                                                           問題45:充電済みコンデンサの並列接続 webadm 2007-9-23 5:21
                                                                                             問題46:充電済みコンデンサの並列接続(その2) webadm 2007-9-24 8:27
                                                                                               問題47:充電済みコンデンサの並列接続(その3) webadm 2007-9-24 9:41
                                                                                                 問題48:変わり種ブリッジ回路 webadm 2007-9-24 10:18
                                                                                                   問題49:電圧を殺す webadm 2007-9-25 5:26
                                                                                                     問題50:偏微分を使った回路解析 webadm 2007-9-27 21:39
                                                                                                       Re: 問題50:偏微分を使った回路解析 webadm 2007-9-28 5:47
                                                                                                       問題51:偏微分を使った回路解析(その2) webadm 2007-9-28 9:45
                                                                                                         問題52:偏微分を使った回路解析(その3) webadm 2007-9-28 11:56
                                                                                                           問題53:ちょっとひねった回路解析 webadm 2007-9-29 6:01
                                                                                                             問題54:ちょっとひねった回路解析(その2) webadm 2007-9-29 19:30
                                                                                                               問題55:ちょっとひねった回路解析(その3) webadm 2007-9-30 2:12
                                                                                                                 問題56:ちょっとひねった回路解析(その4) webadm 2007-9-30 22:24
                                                                                                                   問題57:無限に続く抵抗ラダー回路の解析 webadm 2007-10-3 12:16
                                                                                                                     Re: 問題57:無限に続く抵抗ラダー回路の解析 webadm 2007-10-5 8:30
                                                                                                                       Re: 問題57:無限に続く抵抗ラダー回路の解析 webadm 2007-10-7 3:17
                                                                                                                         Re: 問題57:無限に続く抵抗ラダー回路の解析 webadm 2007-10-7 3:30
                                                                                                                           Re: 問題57:無限に続く抵抗ラダー回路の解析 webadm 2007-10-7 22:30
                                                                                                                             Re: 問題57:無限に続く抵抗ラダー回路の解析 webadm 2007-10-8 5:26
                                                                                                                               問題58:n箇所つながった銅線回路 webadm 2007-10-8 11:12
                                                                                                                                 Re: 問題58:n箇所つながった銅線回路 webadm 2007-10-8 22:24
                                                                                                                                   Re: 問題58:n箇所つながった銅線回路 webadm 2007-10-9 10:27
                                                                                                                                     Re: 問題58:n箇所つながった銅線回路 webadm 2007-10-9 22:18
                                                                                                                                       Re: 問題58:n箇所つながった銅線回路 webadm 2007-10-10 4:19
                                                                                                                                         問題59:漏洩抵抗のある架線を流れる電流 webadm 2007-10-10 5:33
                                                                                                                                           Re: 問題59:漏洩抵抗のある架線を流れる電流 webadm 2007-10-11 3:06
                                                                                                                                             Re: 問題59:漏洩抵抗のある架線を流れる電流 webadm 2007-10-11 4:12
                                                                                                                                               Re: 問題59:漏洩抵抗のある架線を流れる電流 webadm 2007-10-11 5:02
                                                                                                                                                 Re: 問題59:漏洩抵抗のある架線を流れる電流 webadm 2007-10-16 18:24
                                                                                                                                                 Re: 問題59:漏洩抵抗のある架線を流れる電流 webadm 2007-10-17 9:39
                                                                                                                                                   Re: 問題59:漏洩抵抗のある架線を流れる電流 webadm 2007-10-22 0:12
                                                                                                                                                     Re: 問題59:漏洩抵抗のある架線を流れる電流 webadm 2007-10-25 22:12
                                                                                                                                                       Re: 問題59:漏洩抵抗のある架線を流れる電流 webadm 2007-10-26 4:13
                                                                                                                                                         Re: 問題59:漏洩抵抗のある架線を流れる電流 webadm 2007-10-26 4:28
                                                                                                                                                           Re: 問題59:漏洩抵抗のある架線を流れる電流 webadm 2007-10-26 20:24
                                                                                                                                                             Re: 問題59:漏洩抵抗のある架線を流れる電流 webadm 2007-10-26 20:49
                                                                                                                                                               Re: 問題59:漏洩抵抗のある架線を流れる電流 webadm 2007-10-27 11:05
                                                                                                                                                                 Re: 問題59:漏洩抵抗のある架線を流れる電流 webadm 2007-10-27 20:53
                                                                                                                                                                   Re: 問題59:漏洩抵抗のある架線を流れる電流 webadm 2007-10-29 1:45
                                                                                                                                                                     Re: 問題59:漏洩抵抗のある架線を流れる電流 webadm 2007-10-29 10:07
                                                                                                                                                                       Re: 問題59:漏洩抵抗のある架線を流れる電流 webadm 2007-10-30 4:48
                                                                                                                                                                         問題60:短くした電熱線の消費電力 webadm 2007-10-30 9:38
                                                                                                                                                                           問題61:細く短くした電熱線の消費電力 webadm 2007-10-30 10:18
                                                                                                                                                                             問題62:2つの異なる電球を直列につなぐ webadm 2007-10-31 10:39
                                                                                                                                                                               問題63:電力伝送と整合 webadm 2007-10-31 11:07
                                                                                                                                                                                 問題64:電力伝送と整合(その2) webadm 2007-11-1 10:26
                                                                                                                                                                                   問題65:電力伝送と整合(その3) webadm 2007-11-1 10:56
                                                                                                                                                                                     問題66:電池の起電力と内部抵抗を求める webadm 2007-11-1 11:25
                                                                                                                                                                                       問題67:配線抵抗のある電力伝送回路 webadm 2007-11-7 9:49
                                                                                                                                                                                         問題68:電力伝送とマッチング(電源側) webadm 2007-11-7 10:17
                                                                                                                                                                                           問題69:カロリーと電力 webadm 2007-11-7 10:49
                                                                                                                                                                                             問題70:電力量と比熱と融点の応用(フューズ) webadm 2007-11-8 10:54
                                                                                                                                                                                               問題71:電力量と比熱と融点の応用(フューズ)の続き webadm 2007-11-8 11:02
                                                                                                                                                                                                 問題72:合成温度係数 webadm 2007-11-8 11:20
                                                                                                                                                                                                   問題73:抵抗値による温度測定 webadm 2007-11-8 11:40
                                                                                                                                                                                                     問題74:温度係数 webadm 2007-11-8 12:45
                                                                                                                                                                                                       Re: 問題74:温度係数 webadm 2007-11-8 14:07
                                                                                                                                                                                                         Re: 問題74:温度係数 webadm 2007-11-8 14:38
                                                                                                                                                                                                           問題75:膨張係数と温度係数 webadm 2007-11-10 11:29
                                                                                                                                                                                                             問題76:導線の温度上昇 webadm 2007-11-11 13:15
                                                                                                                                                                                                               問題77:温度補償抵抗回路 webadm 2007-11-11 23:25
                                                                             Re: 問題37:Kelvinのダブルブリッジ webadm 2007-9-26 7:48
                                                 Re: 問題26:検流計の内部抵抗を求める Anonymous 2007-5-26 2:32
                                                   Re: 問題26:検流計の内部抵抗を求める webadm 2007-5-26 21:00
                                     誤植発見 webadm 2007-3-25 13:07

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