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MHT-CET : Physics Entrance Exam

MHT - CET : Physics - Magnetic Effect of Electric Current Know More

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  • Galvanometers are instruments used for detecting or measuring current.
  • Moving coil galvanometer and moving magnet type galvanometer are two types of galvanometers.
  • Moving coil galvanometer is further classified into the D'Arsonval or suspended coil type and the pivoted type.
  • Tangent galvanometer is a type of a moving magnet galvanometer.
  • The suspended coil type is more accurate and sensitive while the pivoted type is sturdy, compact and portable.
  • A galvanometer is converted into an ammeter by connecting a low resistance in parallel with the galvanometer coil.
  • A galvanometer is connected into a voltmeter by connecting a high resistance in series with the galvanometer coil.
  • When resistors are connected in series, their effective value increases.
  • When resistors are connected in parallel, their effective value decreases.
  • For a tangent galvanometer, readings are taken between 30 and 60.
  • Accuracy of a tangent galvanometer is maximum for q = 45.
  • Biot Savat's law states that when a current i flows through a small length dl of a conductor, magnetic induction B at a point at a distance r from the element is

B = 



Idl sinq



  • Where
    q = angle between current element and position vector of the point.
    In vector form:







  • The magnetic induction at the centre of a coil of radius r and n turns and carrying current I is

B = 






  • Torque acting on a coil carrying current I when placed in a field of induction B
    t = nI AB sin q
    n = number of turns
               A = area of cross section of coil.

  • Force acting on a charge q moving with a velocity n when placed in a magnetic field of induction B is
    F =
    q vB sin q
    In vector form: 
    q is the angle between  and  .
  • Force acting on a charge of moving with a velocity v when placed in an electric field E is
    F =
    In vector form:

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