# Nonstandard RL circuit

A thin ring with resistance $$R=10~\Omega$$ and self inductance $$L=0.2~\mbox{H}$$ rotates with constant angular speed $$\omega=100~\mbox{rad/s}$$ in an external uniform magnetic field perpendicular to the rotation axis. As a result, the magnetic flux created by the external field varies with time as $\Phi(t)=\Phi_{0}\cos(\omega t) \quad \textrm{where} \quad \Phi_{0}=0.1~\mbox{Wb} .$ Because of the resistance of the ring, energy is being continuously dissipated in the system. What average power $$\bar{P}$$ in Watts must develop the external forces to keep the ring rotating at constant angular speed $$\omega$$ (on average).

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