find the expression for magnetic field induction at the centre of a coil bent in form of a square of side 2a carrying current I.

 hi,

for magnetic field induction at the centre of  coil

the induction due to the parallel sides will add up instead of being cancelled in this case

& induction by all the four sides will be in the same direction either up the plane (  for anticlockwise current flow)  otherwise below the plane 

B = 4 *(  µ./4¶) ( i/ a)(sin Ø_{1^{+ sin Ø}2⁾}

_{^{since Ø} 1  ^{= sin Ø} 2 ^{=  sin 45}} 

    _⁼  4 *(  µ./4¶) ( i/ a)( 2 / 2 ^1/2 )

_⁼  4 * ( 2^ 1/2) *(  µ./4¶) ( i/ a)

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