Q.

A loop ABCDA, carrying current I = 12A, is placed in a plane, consists of two semi-circular segments of radius R1=6 πm and R2=4 πm. The magnitude of the resultant magnetic field at center O is k×10–7 T. The value of k is _______ (Given μ0=4π×10–7 T mA–1)          [2025]


Ans.

(1)

Magnetic field due to AB and CD = 0

B=μ0I2r(θ2π) for an arc

For semi-circule B=μ0I4r

Bnet=μ0I4{4π}–μ0I4{6π}

        =μ0I4π{14–16}

        =10–7×12×224=10–7 T ⇒ k=1