A current I flows through a wire of finite length L. The magnetic field at a distance d from the wire on its perpendicular bisector,
μoI2πdLL2+4d2
μoI4πdLL2+4d2
μoIπd2LL2+4d2
Zero
Point is on perpendicular bisector , so, α = β Field due to finite wire = B=μoI4πdSinα+Sinβ=μoI4πd2Sinα=μoI2πdSinα=μoI2πdLL2+4d2