electron movement in AC

Replies

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  Ramani Aswath

  
  
  Read the section on direct and alternating current here:
  #-Link-Snipped-#
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  somuumos

  sir i got the concept partially but my ultimate doubt is that weather the electron deposits in the positive side as if in the direct current source such as battery of the ac source. And does the same electron electrons flows back and forth through a bulb if connected across a ac source.
• 

  Ramani Aswath

  There is no separate identity for an electron. They are all identical. In a conductor there are free electrons and bound ones. The bound ones remain attached to a particular nucleus and do not move. The free electrons also called conduction electrons keep wandering around randomly when there is no EMF across the conductor. The moment a voltage appears electrons move from wherever they are towards the positive electrode.
  In a DC circuit they end up at the positive electrode of the ultimate power source.
  In an AC circuit they oscillate about a mean position. If the total circuit length is small the distance moved may be enough to let a particular electron to enter the source and be swallowed even in an AC circuit. However, another electron will have to move back in the next half cycle.
  
  I am afraid that the statement that the same electron moves back and forth does not hold water.
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  somuumos

  oh yes sir now i got it. Now some other thing is confusing me, What happens electrons in transmission lines during power transmission.
• 

  Ramani Aswath

  Same thing. Only lot mre electrons are involved. The branches of the distribution system also get into the act. Further in AC power transmission very high voltages are used to minimize line losses. At the use point transformers are used to step down voltages. There is no electron transfer between the primary and secondary of such transformers. The induced magnetic fields cause the secondary circuit electrons to oscillate.
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  somuumos

  ok sir so the final conclusion is that electrons oscillate on their mean position with some frequency. Am I right sir.
• 

  Ramani Aswath

  Yes. That is the way it is Somu forward and reverse. The same way your screen name is.
  You have to keep in mind the total length of the circuit. If the circuit is small and the frequency is low any specific electron may get lost. Even then, the number of electrons going in either direction for each half cycle will be equal.
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  somuumos

  Thank you sir for your patience and care. i have got it clearly. i hope you will show the same interest for clearing my fore coming doubts.
  Regards
• 

  Ramani Aswath

  Once a teacher always a teacher...
• 

  Void Runner

  A.V.Ramani

  I am afraid that the statement that the same electron moves back and forth does not hold water.

  It depends. There are cases when this can happen. In glow discharge plasmas, it is not unusual to see this happen. You apply potential between 2 electrodes. Either of them can conduct and excite electrons for conduction via thermionic or field emission. So, when the potentials are reversed, it is very likely that the reverse process occurs. Under the laws of equilibrium, the system must constantly re-adjust itself to reach an equilibrium point. Generation and recombination of carriers are basically chemical processes that follow Le Chatelier principle.
  
  Practically, in an AC circuit, the electrons cannot move back and forth, because the distance between electrodes is too large and the frequency too high. But electron entering at one end = electron lost at other end and this process is reversed when the input is AC.