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Ok. I am a graduate from electrical engineering. Your questions are basic and fundamental. It's good you can ask such questions
reflecting you have a habit to THINK. pls dont mind if i use English. I will try to make my words simple *** First question: 点解electrons本身有电荷。但如果冇electric supply，就唔能用free electrons的电荷产生电能？*** In conductors (导电体)
there are free electrons. they move in random speed and directions. some electrons move forward but some move backwards. So
the macroscopic effect results in zero NET movement. Electrical supply is like a pump. It pumps the electrons to move in one specific direction. Remember
current (电流) is the flow of electrons. So
you can do nothing with the electrons alone. the electrons have to flow in a specific direction to constitute a current. ***Second question: 点解electrons一定要向正极先有电流？如果open curcuit，free electrons move randomly咁就冇电流？*** The current direction is conventionally defined. In old days
people thought the current flow is due to the positve charge flow. But now we know the current flow is due to the flow of electrons. However
we just stick to the old convention. Hence
we say the current flows from the positive terminal of the battery. In case of open-circuit
the current will have nowhere to flow. you can think this way. In case of open-circuit
the current faces a huge resistance brought by air. In fact
the electrons have no way to flow
resulting zero current. Of course
if the voltage across the open-circuit is high enough
air will be ionized and plete the path of circuit. Current flows in this case. ***third question: 点解电池入面D chemical会用完？用完系因为chemical唔再o系电池入面，抑或D chemical变左另一种matter？*** Basically
the battery we used is chemical battery. Chemical energy is stored in the chemical inside. Through the electrochemical reactions
the chemical energy is converted into electrical energy. However
the chemicals will react each other and another product is formed. Until all reactants are used(直至所有反应物用完)
all chemicals inside will bee a product (生成物). In simple words
when you buy a new battery
there is reactant A inside. When the battery is running low
chemical inside the battery will bee product B. In the process of FROM A TO B
electrical energy is released. In your words
that is **D chemical变左另一种matter** ***Forth question: 点解ammeter在light bulb前或后，测到的electric current系一样？*** the ammeter is connected in series with the light bulb. the current in every point of the series circuit is the same. Hence
the measured electric current is the same. You can think this way. You need to measure how many cars pass through the tunnel. So you can stand at the entrance of the tunnel
or in the middle of the tunnel or even at the exit of the tunnel. The measured results should be the same
unless some cars are crashed inside the tunnel.. **Final question: 点解个curcuit入面冇左light bulb，ammeter测到的electric current大左好多？** there is a tungsten wire inside every light bulbs (traditional one). That wire has huge resistance(电阻). If you take away a bulb
you also take away that amount of resistance. The current now faces less resistance and is happy. So the current should increase. It is simple to understand. If the resistance seen by the current is *** aller
the electrons tend to move more easily. Thank you for reading. Please kindly choose my wer to be the best one if you are happy with my explanation. 2007-03-17 11:56:54 补充： Remember the electrons always move
even without energy supply. The point is the movement is random. the electrons have to unit together and move together in order to constitute a current. Also
I am sorry to say that I found many mistakes and wrong concepts in the first wer
参考: myself
「点解electrons本身有电荷。但如果冇electric supply，就唔能用free electrons的电荷产生电能？」 electrons 不能说动就动，要有能量驱动 「点解electrons一定要向正极先有电流？如果open curcuit，free electrons move randomly咁就冇电流？」 唔系好清楚你问乜。 「点解电池入面D chemical会用完？用完系因为chemical唔再o系电池入面，抑或D chemical变左另一种matter？」 因为D chemical 以经变成 electricity，用左就冇 「点解ammeter在light bulb前或后，测到的electric current系一样？」 因为成个 series circuit current 点都系同一个大细，不同的是 voltage 「点解个curcuit入面冇左light bulb，ammeter测到的electric current大左好多？」 因为 resistance 细左
参考: 自己&朋友
reflecting you have a habit to THINK. pls dont mind if i use English. I will try to make my words simple *** First question: 点解electrons本身有电荷。但如果冇electric supply，就唔能用free electrons的电荷产生电能？*** In conductors (导电体)
there are free electrons. they move in random speed and directions. some electrons move forward but some move backwards. So
the macroscopic effect results in zero NET movement. Electrical supply is like a pump. It pumps the electrons to move in one specific direction. Remember
current (电流) is the flow of electrons. So
you can do nothing with the electrons alone. the electrons have to flow in a specific direction to constitute a current. ***Second question: 点解electrons一定要向正极先有电流？如果open curcuit，free electrons move randomly咁就冇电流？*** The current direction is conventionally defined. In old days
people thought the current flow is due to the positve charge flow. But now we know the current flow is due to the flow of electrons. However
we just stick to the old convention. Hence
we say the current flows from the positive terminal of the battery. In case of open-circuit
the current will have nowhere to flow. you can think this way. In case of open-circuit
the current faces a huge resistance brought by air. In fact
the electrons have no way to flow
resulting zero current. Of course
if the voltage across the open-circuit is high enough
air will be ionized and plete the path of circuit. Current flows in this case. ***third question: 点解电池入面D chemical会用完？用完系因为chemical唔再o系电池入面，抑或D chemical变左另一种matter？*** Basically
the battery we used is chemical battery. Chemical energy is stored in the chemical inside. Through the electrochemical reactions
the chemical energy is converted into electrical energy. However
the chemicals will react each other and another product is formed. Until all reactants are used(直至所有反应物用完)
all chemicals inside will bee a product (生成物). In simple words
when you buy a new battery
there is reactant A inside. When the battery is running low
chemical inside the battery will bee product B. In the process of FROM A TO B
electrical energy is released. In your words
that is **D chemical变左另一种matter** ***Forth question: 点解ammeter在light bulb前或后，测到的electric current系一样？*** the ammeter is connected in series with the light bulb. the current in every point of the series circuit is the same. Hence
the measured electric current is the same. You can think this way. You need to measure how many cars pass through the tunnel. So you can stand at the entrance of the tunnel
or in the middle of the tunnel or even at the exit of the tunnel. The measured results should be the same
unless some cars are crashed inside the tunnel.. **Final question: 点解个curcuit入面冇左light bulb，ammeter测到的electric current大左好多？** there is a tungsten wire inside every light bulbs (traditional one). That wire has huge resistance(电阻). If you take away a bulb
you also take away that amount of resistance. The current now faces less resistance and is happy. So the current should increase. It is simple to understand. If the resistance seen by the current is *** aller
the electrons tend to move more easily. Thank you for reading. Please kindly choose my wer to be the best one if you are happy with my explanation. 2007-03-17 11:56:54 补充： Remember the electrons always move
even without energy supply. The point is the movement is random. the electrons have to unit together and move together in order to constitute a current. Also
I am sorry to say that I found many mistakes and wrong concepts in the first wer
参考: myself
「点解electrons本身有电荷。但如果冇electric supply，就唔能用free electrons的电荷产生电能？」 electrons 不能说动就动，要有能量驱动 「点解electrons一定要向正极先有电流？如果open curcuit，free electrons move randomly咁就冇电流？」 唔系好清楚你问乜。 「点解电池入面D chemical会用完？用完系因为chemical唔再o系电池入面，抑或D chemical变左另一种matter？」 因为D chemical 以经变成 electricity，用左就冇 「点解ammeter在light bulb前或后，测到的electric current系一样？」 因为成个 series circuit current 点都系同一个大细，不同的是 voltage 「点解个curcuit入面冇左light bulb，ammeter测到的electric current大左好多？」 因为 resistance 细左
参考: 自己&朋友
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