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Faraday's law

  1. Jan 1, 2014 #1
    what will be the direction of current at 'P' point in the transformer?

    Attached Files:

  2. jcsd
  3. Jan 1, 2014 #2
    Since you have the symbol for DC voltage on your schematic, the answer is that there isn't a current there.

    If you meant AC, to the right. Basically the second solenoid is an upside down version of the first, with magnetic field pointing down.
  4. Jan 1, 2014 #3
    But what will be the direction of current at point p
  5. Jan 1, 2014 #4
    Can you tell the direction of current at point p?
  6. Jan 1, 2014 #5
    Look up "Lenz law";

    "An induced electromotive force (emf) always gives rise to a current whose magnetic field opposes the original change in magnetic flux."
  7. Jan 1, 2014 #6
    So as per this definition the direction will be outside? Am I right?
  8. Jan 1, 2014 #7


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    outside what ?

    did you understand mishima's comments in post 2 ?

    that is did you really mean to show AC and not DC as you did ?

  9. Jan 1, 2014 #8
    On primary side the current in the coil is flowing in anti clock-wise direction, therefore the flux(mean flux path) will be upward in the first limb, but this same flux will be passing in the secondary side in the downward direction so how will we find the direction of current in it.
  10. Jan 2, 2014 #9


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    with the DC as you have shown, there will only be a very brief moment that current will flow in the secondary coil
    and it will be in the opposite direction to the current flowing in the primary.
    As soon as the current and hence the magnetic field in the primary reaches maximum ( and no longer varies)
    current will stop flowing in the secondary.

    Do you understand why?

    Last edited: Jan 2, 2014
  11. Jan 2, 2014 #10
    Ok fine but will happen if we take direct current?
  12. Jan 2, 2014 #11
    View attachment New Doc 1.pdf

    yes, because in starting the voltage increases but when it reaches its maximum value then the changing flux saturates and therefore there is no rate of change of flux and hence current will stop flowing in the secondary.
    but my doubt is where we are using the Faraday's law in this case if i take the ac supply and the current and flux is as i shown in the attachment(let me know if it is wrong and why).
    please elaborate and implement the Faraday's law in this figure.
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