以前理化課教到電流時，都會提到
所謂的電流方向與電子流方向是相反的。然後因為人們最初誤會了電荷流動的方向，所以我們不小心把電子移動的反方向當作是電流方向了。
嗯，所以我想分享一些我對這段物理史的了解，我們都誤會了「古人」。其實就當下發展脈絡而言，這些物理學家並沒有搞錯什麼，而是我們搞錯了什麼。
底下原文來自：Ampère lays the foundations of electrodynamics (September 1820-January 1821)
The intensity of the current being gauged, if not measured, by the angle of the needle’s deflection, how did one define the “direction” of the current? Ampère’s initial idea about the nature of the current in the metallic wire was that there existed two simultaneous and opposite currents of positive electricity and negative electricity.
雖然我們可以從磁針偏轉程度來估計電流大小，但我們又該如何定義電流的方向呢？最初，安培將金屬導線中的電流視為是由兩種共存的反向正電流與負電流所構成的（參見：電的流體理論）。
He arbitrarily chose to call the direction of the current that of the positive electricity. What relationship was there between this – conventional – direction of the current and the magnetic effect? Ampère stated a simple rule that avoided the long list that Oersted made of the various possible scenarios:
接著安培就將 “current” 一詞用來指涉 “positive electricity”。那接下來的問題就是，所謂的 “current”（正電）方向究竟跟我們觀察到的磁效應有什麼關係？於是安培就提出了一個簡單的規則，以取代掉奧斯特當時提出的對於各種情境下的電流方向定義。
“If one mentally stands in the direction of the current in such a way that it flows from the feet to the head of the observer, and one’s face is turned toward the needle, it is always to one’s left that the action of the current will divert [the north pole of the needle] from its normal position.”
「想像（正）電流就從你的腳底流到你的頭頂，然後你面向前方的磁針，並且磁針總是因正電流的磁效應而向你的左方偏轉。」
Ampère drew his “observer” for the case of electric currents that he imagined inside the terrestrial globe. The circle represents the Earth with its magnetic poles N(orth) and S(outh) connected by a terrestrial meridian. The observer is traversed from foot to head by an electric current (partially shown) circulating around the equator. One must imagine the observer lying on his back on the ground and watching a compass located above him. His left arm indicates the direction that will be taken by the North pole of the compass under the action of the current, that is to say the N(orth) pole of Earth.
Ampère’s “little guy” (le “bonhomme d’Ampère”) has incited generations of French lycée students to all sorts of contortions, at least mentally, and at times stimulated their humorous wit.
安培為此畫了張圖案，如右圖。他說地球裡面就像是有這種電流，繞著地球赤道自轉，所以才產生了南北極。 圖中的圓圈就是地球，子午線連接著南北極。電流就從安培想像的觀察者的腳底流向頭頂，並持續地繞著赤道轉了一圈（人只不過是赤道的一部份）。這差不多就像是你躺在地板上看著天空，然後眼前（空中）扶著一個磁針。這時磁針N極就會指向他的左手，也就是說左手指向北極。
事實上右手大拇指就是「小男孩的臉」，四指則代表「小男孩面前的磁針N極轉向」。
於是，我們都誤會了安培右手定則。傳統的安培右手定則的教學方法告訴我們「可以由電流判斷磁場方向」，但其實安培是用觀察得到看得見的磁針偏轉方向，定義了電流方向；安培右手定則並非用電流判斷磁針偏轉方向，而是用磁針偏轉方向定義電流方向。
最後在我們了解電子概念後，才了解原來電子運動方向跟上述方法定義的電流方向是相反的。
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