Put a parallel metal guide rail in the uniform magnetic field, and the guide rail is connected with the large coil m, as shown in the figure. Put a wire AB on the guide rail, and the magnetic induction line is perpendicular to the plane of the guide rail. In order to make the small closed coil n surrounded by M produce clockwise induced current, the motion of the wire may be () A. Uniform right movement B. accelerated right movement C. uniform left movement D. accelerated left movement

Put a parallel metal guide rail in the uniform magnetic field, and the guide rail is connected with the large coil m, as shown in the figure. Put a wire AB on the guide rail, and the magnetic induction line is perpendicular to the plane of the guide rail. In order to make the small closed coil n surrounded by M produce clockwise induced current, the motion of the wire may be () A. Uniform right movement B. accelerated right movement C. uniform left movement D. accelerated left movement

A. When the wire AB moves to the right at a constant speed, the induced electromotive force and induced current generated by the wire AB remain constant, the magnetic field generated by the large coil m remains constant, and the magnetic flux passing through the small coil n remains constant, so there is no induced current generated; B. When the wire AB accelerates to the right, the induced electromotive force and induced current generated in the wire AB increase. According to the right-hand rule, the direction of AB current is from a to B. according to the ampere rule, the direction of magnetic field generated by M is perpendicular to the paper surface, and the magnetic flux passing through n increases. According to Lenz's law, the induced current generated by coil n is counterclockwise, which is not in line with the meaning of the problem Therefore, error B. & nbsp; & nbsp; & nbsp; C. when wire AB moves to the left at a uniform speed, the induced electromotive force and induced current generated by wire AB remain constant, the magnetic field generated by large coil m remains constant, the magnetic flux through small coil n remains constant, and no induced current is generated, which is not in line with the meaning of the problem; D. When the wire AB accelerates to the left, the induced electromotive force and induced current generated in the wire AB increase. According to the right-hand rule, the direction of AB current is from B to A. according to the ampere rule, the direction of magnetic field generated by M is perpendicular to the paper surface and outward, and the magnetic flux passing through n increases. According to Lenz's law, the induced current in the clockwise direction generated by coil n is consistent with the meaning of the problem Correct. So choose D

Put a metal bar on the U-shaped smooth guide rail, total resistance R, magnetic field B, given initial velocity V0, how long does it take to stop
I figured it out to be positive infinity, but there's a limit stop

That's it. It's a limit problem~