# Energy conservation in induced emf in open loop

We have a closed loop in the influence of magnetic fields of electromagnets somewhat like this. (Kindly ignore the currents and forces shown - the coil is stationary and initially no current flows)

The magnets now rotate around the coil and an emf is induced in the coil. The circuit being closed, induced current results. The power dissipated i^2R comes from the power used by the external agency to cause the change of flux, in this case rotation of the electromagnets. But if the loop is open and the induced emf cannot result in an induced current, how does the energy of the external agency appear in the circuit? Is the emf generated itself a way to store that energy which expresses itself when current flows? But if this were to be true, the emf should have kept on increasing as the external agency would continue to supply energy, but this is contrary to Faraday's law as the emf would increase only if the rate of rotation of magnets would increase. So, the crux is, where does the energy used to rotate the magnets go when the circuit is open?

The power produced by the engine still remains equal. The angular speed decreases as torque applied by the engine increases (Power = Torque $$\cdot$$ angular speed)