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Conventional current

  1. Nov 14, 2004 #1
    Just a couple of questions on conventional current that have been troubling me...

    Firstly, does conventional current = electric current? I saw a question on a past exam that had "electric" current in a cable flowing from north to south, and asked to determine the direction of the magnetic field directly above the cable. The answer was west - so thus electric current == conventional current?

    Secondly, if it is not stated on diagrams which show the direction of current, should it be assumed that it is depicting conventional current?

    Thanks in advance

  2. jcsd
  3. Nov 14, 2004 #2
    I'll try my best to these questions.
    Electric current means the rate of flow of charge(in coulomb) passing through a given cross-section of a conductor. Conventionally, Its direction is taken to be positive to negative, opposite to the REAL direction of current but it is equal in magnitude to it. In most of the questions the word 'electric current' refers to conventional current, unless stated otherwise. In the question you asked, by applying right hand rule, the answer 'west' is only possible if the electric currect refers to conventional current. Thus, it confirms that here Electric currect does mean conventional current.
    Lastly, Yes, if the question does not state otherwise, the direction of the flow of electic current shown in the diagram is the direction of conventional current.
    Hope this helps. :smile:
    Ab. S.
    Last edited: Nov 14, 2004
  4. Nov 17, 2004 #3
    Up to you

    In electronic circuit diagrams it does not matter which convention you use so long as you are aware of the polarity requirements of the components , that is you cannot connect polarised capacitors or transistors just any way you want. Conventional or real is just a mental state -- electrons flow from -ve to +ve and holes flow from +ve to -ve irrespective of how you visualize this
    but you better connect the collector of an npn transistor to the +ve supply
    and it's emitter to the -ve , otherwise it may still work but at 1/100th of it's capability.
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