If i= 2A and R=0.4 m, find the magnetic moment at O, the common centre of the arcs.

Explanation

Area of upper portion of semicircle,
`A_(1)=(pi R^(2))/(2)=(pi xx (0.4)^(2))/(2) = 0.25 m^(2)`
Area of lower portion of semicircle,
`A_(2)=(pi((R )/(2))^(2))/(2)=(pi ((0.4)/(2))^(2))/(2) =0.063`
`:.` Moment `= i xx (A_(1)+A_(2))`
`=2(0.25 +0.063) =0.626"A-m"^(2)`