# Biot

**Topics:**Magnetic field, Electromagnetism, Electric current

**Pages:**2 (369 words)

**Published:**October 18, 2012

Biot-Savart’s law deals with the magnetic field induction at a point due to a small current element. Current element

A current element is a conductor carrying current.It is the product of current,I and length of very small segment of current carrying wire ,dL. Let us consider a small element AB of length dl of the conductor RS carrying a current I. Let r be the position vector of the point P from the current element I dL.and θ be the angle dl and r. According to Biot-Savart’s law,the magnetic field induction dB or magnetic flux density at a point P due to current element depends upon the following factors. (i) dB∞I

(ii) dB∞dl

(iii) dB∞sinθ

(iv) dB∞1/r2

Combining these factors,we get

dB∞IdLsinθ/r2

or dB=K Idl sinθ/r2 where K is a constant of perportionality.

In S.I units, K=μ0/4π thus , dB=μ0/4π I dl sinθ/r2 where μ0 is absolute premeability of free space and

μ0=4π*10-7 Wb A-1m-1

= 4π*10-7*TA-1m [ 1T=1 Wb m-2] In C.G.S units,K=1 (In free space)

Thus dB=Idl sinθ/r2

In vector form,

dB=μ0/4π I(dl*r)/r3

magnetic field induction at point P due to current through entire wire is B=∫μ0/4πIdl*r/r3

Or B=∫μ0/4π Idl sin θ/r2 BiotSavart’s law in terms of magnetising force or magnetic intensity (H) of the magnetic field: In S.I System,

dH=dB/μ0=1/4π Idl*r/r3=1/4π Idl*αr/r2

H=∫1/4π Idl*αr/r2

H= ∫1/4π Idl sinθ/r2

Importance OF BIOT SAVART’S LAW:-

1. This law is analogous to Coulomb’s law in electrostatics. 2. Biot Savart’s law is valid for a symmetrical current distribution. 3. This law cannot be easily verified experimentally as the current carrying conductor of very small length cannot be obtained pratically. 4. Biot Sarvart’s law is applicable...

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