Discussion in 'Homework Help' started by Roshela_kyoot, Oct 6, 2005.

  1. Roshela_kyoot

    Thread Starter New Member

    Oct 6, 2005
    Hi! roshela, im an ECE student, i have some questions...
    1) what is the relationship between current in a wire and a magnetic field?
    2.) how does the amount of current in the coil and the type of material affect the strength of an electromagnet?

    ---i really need some answers for my lab report...
  2. haditya

    Senior Member

    Jan 19, 2004
    the relationship between current in a wire and a magnetic field (in the case magnetic induction or magnetic flux density) is given by biot-sevart's law

    B= ∫ (υ/4pi) (i*dl*sin θ )/(r*r)
    where b is the magnetic induction
    dl is a differntial length of conducting element
    i is the current thru the differntial length of conductor
    r is the distance of a point from the wire at which B is measured
    (υ) is the permeability of the medium
    direction of B is given by the Right hand screw Rule for cross product of vectors

    in vector form the equation is given by

    B = ∫ (υ/4pi)(i* dl*r)/(r*r*r)

    dl is the vector representing the length dl in the direction of current i
    r) is the radius vector directed from the differential element dl to the point at which B is measured

    As you can see the value of B is indeed dependent on the value of i and the value of υ (which depends on the medium ) the value of B in iron (a ferromagnetic material) is much greater than the value of B in free space..thats why we use an iron core in electromagnets
    the value of B in turn determines the strength of the electromagnet
  3. Dave

    Retired Moderator

    Nov 17, 2003