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wire tension



A circular loop of flexible wire is placed in a uniform
magnetic field perpendicular to its plane. The radius of
the loop is R and its current is I. What is the tension?
The end of the book answer is: T=I*B*R.

How can this be derived? I know that each dL element
is subjected to the radial outward force B*I*dL. But
tension is a tangential force. Intuitively I do expect tension
to be proportional to the radial force per unit length (I*B)
but I do not know how to demonstrate that T=I*B*R.
Ludwik Kowalski