Chapter: Physics : Effects of electric current : Higher Secondary(12 Std)
Current loop as a magnetic dipole
Current loop as a magnetic dipole
Ampere found that the distribution
of magnetic lines of force around a finite current carrying solenoid is similar
to that produced by a bar magnet. This is evident from the fact that a compass
needle when moved around these two bodies show similar deflections. After
noting the close resemblance between these two, Ampere demonstrated that a
simple current loop behaves like a bar magnet and put forward that all the
magnetic phenomena is due to circulating electric current. This is Ampere’s
hypothesis.
The magnetic induction at a point
along the axis of a circular coil carrying current is
The direction of this magnetic field
is along the axis and is given by right hand rule. For points which are far
away from the centre of the coil, x>>a,
a2 is small and it is neglected. Hence for such points,
Hence a current loop is equivalent
to a magnetic dipole of moment M = IA
The magnetic moment of a current
loop is defined as the product of the current and the loop area. Its direction
is perpendicular to the plane of the loop.
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