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We have a metallic wire circular loop of resistance $R$, having radius $a$, placed in a magnetic field $\bf{\vec{B}(t)}$. The magnetic field is perpendicular to the plane of the wire.
The magnetic field is uniform over space, but magnitude decreases with time at a constant rate $k$ and $k=-\frac{d|\bf{\vec{B}(t)}|}{dt}$.
What will be the $\bf{tension}$ in the metallic wire?
The tension U(t) is proportional to the time-derivative of the magnetic flux trough the wire (Faraday law):
$$U=\int_{\rm Wire} \vec E.d\vec\ell=-{d\over dt}\int_{\rm Disk} \vec B.d\vec S$$
In your case, this simplifies into
$$U=-{dB\over dt}S=k\pi a^2$$
The resistance $R$ fixes the intensity (through Ohm law), not the tension.
$\begingroup$The tension is the tensile force on the wire. From the EMF and resistance you can compute the current in the wire. From the current and magnetic induction you can then compute the tension in the wire.$\endgroup$
