CBSE Class 12 Physics Magnetic Effects of Electric Current Exam Notes

CBSE Class 12 Physics Magnetic Effects of Electric Current Exam Notes Please refer to the examination notes which you can use for preparing and revising for exams. These notes will help you to revise the concepts quickly and get good marks.

Oersted in 1820 by observing the deflection of compass needle when it is brought near a current carrying conductor discovered that a current carrying conductor produces magnetic field in space surrounding it. This field is described by vector B called magnetic induction, flux density or simply field vector with units Wb/m2 or tesla. In case of current carrying conductor it is computed either with the help of Biot-Savart law or Ampere’s law.
Biot Savart law is magnetic analogue of Coulomb’s law while Ampere’s law is analogous to Gauss’s law.

BIOT-SAVART LAW
This law provides a method for calculating the magnetic induction at any point in space around a conductor carrying a current. If a small element of length dl of a long conductor carries a current I, the magnetic field or magnetic induction dB at any point P at a distance r is given by Biot-Savart law as

H = B/μ or B = μ H
where μ is permeability of the medium. The unit of magnetic intensity H is ampere / metre.

Maxwell’s Cork Screw Rule: If a right handed cork screw is rotated so that its tip moves in the direction of flow of current through the conductor, then the direction of rotation of the head of the screw gives the direction of magnetic lines of force.

Right Hand Rule :If the conductor is held in the right hand such that the thumb points in the direction of the current, the direction in which the fingers curl gives the direction of the magnetic field.

APPLICATIONS OF BIOT-SAVART LAW
1. Magnetic Induction due to Long Straight Current Carrying Conductor : Consider the current I flowing through a long current carrying conductor. If a small element CD of the conductor
has a length dl, then the field dB at P due to this conductor is given by Biot-Savart law as :

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