Q.

An element l=xi^ is placed at the origin and carries a large current I = 10 A. The magnetic field on the y-axis at a distance of 0.5 m from the element x of 1 cm length is ______.                [2024]

1 8×10-8 T  
2 10×10-8 T  
3 4×10-8 T  
4 12×10-8 T  

Ans.

(3)

By Biot-Savart law, dB=μ0i4π(dl×r)r3  (Tesla)

Since element is very small,

Given: dl=1100i^m,  r=12j^m,  i=10 A,  θ=90°

=10-7×10×(1100i^×12j^)(12)3

=10-7×10×8200k^=4×10-8 T(+k^)