two concentric rings of radii `r` and `2r`are placed with centre at origin. Tow charges ` +q` each are fixed at the diametrically opposite points of the rings as shown in figure . Smaller ring is now rotated by an angle ` 90^@` about Z-axis then it is again rotated by ` 90^@` about Y-axis . Find the work done by electrostatic forces in each step . If finally larger ring is rotated by `90^@` about X-axis , find the total work required to perform all three steps .
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Answer

`W_("fist step")=(8/(3)-(4)/(sqrt(5)))(Kq^(2))/(r),W_("second step")=0,W_("total")=0`