Magnetic Force Between Two Coaxial Square Coils Carrying Currents

In order to achieve the magnetic force between two coaxial square coils canying currents,the coefficient of mutual induction is computed.Then principle of virmal work is employed as a handy way to calculate the force.The extreme value property of the force is analyzed and illustraed.The preeminent mechanical state where no magnetic tension force exerts on either of the two concentric square coils carrying currents is described.