Check this one out in the Variables vs Time view. You will see the initial large displacement provided by the initial conditions cause the strip to undergo some initial vibration at its natural frequency while the high frequency force imposed by the electric current causes a high frequency component of the motion. As the initial transient dies away, the magnetic force causes a very small amplitude movement at the frequency of the forcing function. Basically the forcing function is changing so rapidly that it does not have time to have much effect on the strip.