電流的問題 關於電流的改變

相信你講緊係串聯電阻，串聯電路電流係不變，但電壓就會改變。舉例，電源電壓係10v，負載係10歐，如果冇其他串聯電阻，電流就係1a，當加上10歐串聯電阻，總負載變成20歐，電流就只得一半，500ma。如果你問仲有500ma去咗邊﹖可以咁講，仍然保留係電源能量，所以你話電阻改變電流係對嘅，但更確切係負載改變電流，要留意負載(loading)一詞，以電阻值計，負載同電阻成反比，但同電流成正比。

Electric current in a conductor is the flow of electrons. The numbner of electrons that enter into a resistor must be equal to the same number of electrons leaving the resistor (Law of Conservation of Mass, because electrons have mass). Therefore, the flow of electron, and hence the current remains the same before and after a resistor.

You seems to have misunderstanding on the meaning of resistance. The resistance in a circuit governs the number of electrons flowing in the circuit. That said, a low resistance allows more number of electrons flowing, whereas a high resistance allows less number of electrons flowing. But the number of electrons passing through a given resistance is fixed.


2011-10-16 13:55:36 補充：
Your suppl question: 如果電流是為2A, 即使流過電阻器,通過B點,通往正極方向,但為甚麼電流仍保持2A?
Ans: 2 A current means there are 1.25x10^19 electrons (of total chagre 2 coul) passing through the resistor in one second. Each of these electrons would not suddenly disppear....

2011-10-16 13:57:07 補充：
...You would then expect there are still 1.25x10^19 electrons leaving the resistor in one second. That's why the current is still 2A. This is only the result of conservation of mass (物質守恆定律).

2011-10-16 14:00:58 補充：
This is similar to water passing through a pipe. The mass of water per second entering into the pipe must equal to the same mass leaving the pipe. Just imagine electron current (flow of electrons) similar to the flow of water, you would understand it more clearly.

2011-10-16 14:04:27 補充：
Be aware that the change of "potential" of electrons after passing through a resistor doesn't affect the "number" of electrons that flow. This is similar to the case of water flowing in a pipe, in which only the "pressure" of water decreases but not the "mass" of water.

In a series circuit, the current keeps constant.