問交流電流向

1.將粒磁石放喺漆皮線圈中間，轉動磁石，會產生交流電，咁如果將電路斷開，照樣轉動磁石，導線（漆皮線）內又會否有電？

A: No. There will not be any current in an open circuit (開路). But be aware that there is still emf (electromotive force)(電動勢) induced on the coil by the rotating magnet. This is just similar to a battery connected to an open circuit.

2.點解將導線串聯一d負載（例如燈泡）並閉合，再轉動磁石，粒磁石會比起電路斷開嘅時候難轉？

A: This is simply conservation of energy (能量守恆). The load consumes energy (e.g. the bulb gives out light), but the enrgy comes from the work done in rotating the magnet.

3.交流電嘅負半弦係咪指電流由中線經負載，再流返去火線？
定係用電時，只係會用到正半弦？

A: A load (負載) without definite polarity (極性)(e.g. a light bulb) consumes both the -ve and +ve cycle of the sinusoidal current. Those with definite polarity only consume half (either the +ve or -ve) of the cycle .

4.電子流是否會由地球流向中線，以做回路？

A: The neutral line is kept at earth potential (地電位). In principle, there is no current flowing between places of the same potential.


2014-08-07 00:14:36 補充：
Q:如果中線係保持0電壓,咁交流電下半週既負電壓係由邊度嚟?
A: It comes from the voltage variation of the Live wire. During the +ve half cycle, the Live wire is at volage higher (i.e. +ve voltage) than the Neutral wire (earth potential), and it is at volrage lower (i.e. -ve voltage) than the Neutral wire in the -ve half cycle.

1.磁場切割線圈就會生電，如果線圈開路，只會有壓冇流。

2.當線圈閉合後，有電流流通，但電流流過線圈亦會產生磁場，線圈磁場與磁石磁場互相作用，所以轉動磁石時有阻力。

3.交流電上下半週都會通過負載。

4.市電用中線做回路。