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B About Transformers

  1. Jun 30, 2016 #1
    As I understand in transformer when there are two sections of wire, changing magnetic field induces voltage into another wire.

    Can anyone tell why induced voltage depends on how many loops of coil there are ?
    Less loops of coil there are in secondary coil, less voltage will there be induced by magnetic field.
  2. jcsd
  3. Jun 30, 2016 #2


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    welcome to PF :smile:

    have an educated guess
    lets take a primary coil with a fixed number of turns, it's going to generate a magnetic field of a certain strength

    now within that magnetic field a coil of 10 turns and a coil of 100 turn
    in which coil will a greater EMF be generated and why ?

    google Faraday's Law for some ideas
    then come back and let us know what you found and how to answer the above question

  4. Jul 1, 2016 #3
    Hi, and this is what I have found: Generated voltage equals to -N times ΔΦ/Δt, where ΔΦ=AB ( A - area of coil, B - external magnetic field, N - number of turns).
    In a coil of 100 turn there will be 10 times more voltage generated compared to coil of 10 turns, according to that formula. Why it depends on the number of turns though ?

    Maybe I am formulating the wrong question because I don't really understand this at present. When a changing magnetic field is generated in one coil and there is a second coil in its vicinity - current will be induced. Now which scenario occurs for the second coil when magnetic field changes ?

    1. Changing Magnetic field -> Electric field -> Current (moving electrons)
    2. Changing Magnetic field -> Current ?

    If its the 1st one, then could it be that generated electric field is in turn produced by individual electric fields around each turn of coil interfering with each other ? (like with magnetic fields around each turn in inductor that interfere and overlap to produce stronger field)
  5. Jul 1, 2016 #4


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    Think it through ... what does a 100 turn coil have that a 10 turn coil doesn't have ?
    and with that, what is the effect of the magnetic field on the 100t coil compared to the 10t coil ?

    yes, but it is a little more complex than that and you don't have to go that deep to understand the basics

    simply, a changing magnetic field generates a changing electric field and so on ... this is an electromagnetic field

  6. Jul 1, 2016 #5
    Thanks for responses. I think 100 turns has more conductive materiel in magnetic field. Although isn't it already covered with the A - area of coil in the formula ? In that case what brings N to the table.

    I wasn't sure about this, so does it mean whenever there is a changing magnetic field, electric field is generated and that electric field creates the voltage that forces electrons to move (current), am I understanding this right ? (without going to Einstein's relativity I was wondering if I am understanding the mechanics here just in simpler magnetic and electric fields).

    If this is right (changing magnetic field ->generated electric field->induced voltage and current), maybe form of the coil matters (N, turns) because of electric fields around turns somehow overlapping with each other and creating a general strengthen electric field ? I am thinking of an analogy of current running through an inductor where individual magnetic fields around each turn overlap and create a greater, general magnetic field. Otherwise I am not sure. I just don't understand why form of the coil (and even area of the coil) would contribute to the strength of the generated electric field (and hence strength of the voltage) in the secondary coil by the changing magnetic field from the primary coil.
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