Electrical Engineering ⇒ Topic : Biot-Savart Law and its important points.
Biot-Savart law gives us expression for the magnetic field at a point due to a current element.
Important points about Biot-Savart law. This law has the following salient features :
(1) Biot-Savart law is valid for symmetrical current distributions.
(2)Biot-Savart law cannot be proved experimentally because it is not possible to have a current carrying conductor of length dl.
(3) Like Coulomb's law in electrostatics, Biot-Savart law also obeys inverse square law.
(4) The direction of dB is perpendicular to the plane containing I dl and r
Magnetic Field Intensity (H) due to a Current Carrying Element - Biot-Savart Law
If an element of length dl of a conductor, measured in the direction of current flow, carries a current of I amperes, then the magnetic field intensity at a point P at a distance r from the element is given by
dH = I d 1 x r l 4 π r3 ........... (1)
FIGURE (a) Magnetic field intensity (H) due to the flow of electric current
where, dH is a vector perpendicular to the plane determined by dl are r as shown in Fig. (a). The value of dH depends on the cross product and therefore changes its sign if the direction of flow is changed.
Equation (1) gives H in A/m when l is in amperes and dl and r are in metres.The value of dH depends upon the position of point P, and is zero when P lies in line with the element. The direction of dH changes as P moves over to the other side of the element as shown in Fig. (b).
figure (b) Magnetic field intensity (H) on either side of a current carrying element
Any current carrying conductor must be a closed loop in order to carry the current and the total magnetic field intensity produced by such a loop of wire is given by
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