BIOT SAVART LAW
BIOT SAVART LAW

    Consider a long straight conductor carrying current I. Then magnetic field is in the form of circle.

    BIOT SAVART found that the magnitude of field B is directly proportional to twice of current I and     inversely proportional to the distance r.

B a 2I

And
B a 1/r

B a 2I/r

B = mo/4p.2I/r

    mo is called permeability of free space.
     mo/4p is proportionality constant. Its value is 10-7.
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AMPERE’S LAW

    STATEMENT:

    This law states:

    "The sum of products of tangential component of B and length element Dl of a closed curve is mo     times the current enclosed."

    mo = permeability of free space.

    Its value is 4p*10-7.

    Its unit is Henry/m2.

    Mathematically.

S(B.Dl) = moI
PROOF OF AMPERE’S LAW
 

Let the circular field B be divided in to small elements Dl. Now tangential component of B

Bx = BCosq
    Multiplying length element Dl with tangential component of B, we have,

B. Dl = BCosq. Dl

But, q is negligible i.e. q = 0

B. Dl = BCos(0o). Dl

B. Dl = B (1) . Dl

B. Dl = B. Dl

    For the complete curve, the sum of their products will be,

SB. Dl = SB. Dl

= BS. Dl

but, B = mo/4p.2I/r

and SDl = 2pr

SB.Dl = mo/4p.2I/r x 2pr

SB.Dl = mo x I

    This is mathematical form of Ampere’s law.
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