Faradays Law for Induced EMF

Discussion in 'General Electronics Chat' started by jagjit Sehra, May 7, 2008.

  1. jagjit Sehra

    Thread Starter Member

    Feb 29, 2008
    Hi Folks,
    Got a question regarding using Faradays Law to calculate the induced EMF. I know there is a fundamental problem with my understanding of this area so please be gentle with me.

    Faradays Law is as follows:

    e = -N d (AB cos 0) / dt (I have use 0 to denote theta)

    I have also seen the equation as follows:

    e = NAB sin 0 (This is the derivative of the first equation (Is that right))

    This suggests that if a conductor is placed in a magnetic field it will induce a current. Also if the conductor is moved once in the magnetic field it will also induce a current. However if the conductor is moved parallel to the direction of the magnetic flux there will be zero induced voltage as there is no cutting on the magnetic flux (there is a zero angle difference and sin 0 is 0 therefore e = 0). When the conductor is at 90 degrees there is maximum induced current as the cutting of the flux would be maximum at that point.
    Firstly I would like someone to confirm that I am correct with what I have stated above. If I am that raises another question for me, if the conductor was placed inside a magnetic field where the conductor is parallel with the magnetic flux i.e. there is no cutting of the flux then the equation would suggest that no EMF is induced in the conductor but surly it would.

    Can one of you good people help me to overcome my confusion, Thank you in advance?

  2. thingmaker3

    Retired Moderator

    May 16, 2005
    (Note: You can click on the "\Sigma" icon above the post window when you want to use Greek letters or other math symbols.)

    You are correct on all counts. There must be relative movement between the field and the conductor in order for EMF to be induced. A conductor moving in the same direction as the flux lines, or moving in any direction when parallel to the flux lines, will have negligible EMF induced.
  3. jagjit Sehra

    Thread Starter Member

    Feb 29, 2008
    Hi, Thanks a lot for your reply, But I am still not sure do you mean that when if the conductor is placed into a magnetic flux and is in parallel with the flux then from the Faradys equation:

    e = NAB sin \theta

    then the sin \theta part is ignored because if it isnt then the induced voltage would be zero. Also in that case the same special method would apply if the conductor was taken out of the field assuming it was in parallel with the flux.

    Thanks in advance!
  4. recca02

    Senior Member

    Apr 2, 2007
    For a emf(current depends on configuration of circuit i.e closed,open,etc.) to be induced, there has to be a change in the magnetic environment. Just keeping a coil in magnetic field is not enough, there must be changes in magnetic flux linked to the coil by either moving the coil or the field.