(1) if the metal rod ab vertical upward motion, the metal rod does not cut the magnetic induction, will not produce induced current, this time the sensitive ammeter needle does not deflect;
(2) if the metal rod ab horizontal to the left, the metal rod cuts the magnetic inductance, resulting in an induced current, at this point, the sensitive ammeter needle deflection
(3) Keep the metal bar ab immobile, when the U-shaped magnet moves horizontally to the right, the relative motion between the metal bar and the magnetic field occurs, the metal bar also cuts the lines of magnetic susceptibility, producing an induced current, at this time, the sensitive ammeter pointer is deflected.
The answer is: no deflection; deflection; deflection.
The answer is: no deflection; deflection; deflection.