(1) The induced current is generated by the movement of the conductor cutting the magnetic induction line in the magnetic field. On the premise that the magnetic field has been guessed, we should guess from the movement that the magnitude of induced current may be related to the speed of conductor movement.

Main steps: A. Let the conductor ab move slowly to the right in the magnetic field. Observe the deflection angle of the sensitive galvanometer pointer.

B, let the conductor ab move to the right at a faster speed in the same magnetic field. Observe the deflection angle of the sensitive galvanometer pointer.

C. By comparing the deflection angles of two sensitive galvanometers, we can know the relationship between the induced current and the velocity of the conductor.

(2) Because the multi-turn coil moves in the magnetic field, it is equivalent to cutting the magnetic induction line by multiple wires at the same time, that is, it is equivalent to connecting multiple power supplies in series, so the current in the circuit is larger, that is, it is larger in (a), so choose A;

(3) We know that conductor cutting magnetic induction line can produce induced current, that is, there is relative motion between conductor and magnetic field; In this topic, the magnetic field movement can be considered as the movement of the wire relative to the magnetic field, so it can also produce induced current; The induced current should be related to the strength of the magnetic field, the slow motion of the magnet and the number of turns of the coil.

(4) The direction of induced current is related to the cutting direction and the magnetic field direction, so both of them can change the direction of current by changing the magnetic pole and the direction of motion.

Namely ① changing the cutting direction (or changing the magnetic pole direction); ② Change the direction of magnetic pole (or change the direction of magnet movement)

So the answer is: (1) the speed of conductor movement; Main steps: A. Let the conductor ab move to the right at a slow speed in the magnetic field. Observe the deflection angle of the sensitive galvanometer pointer. B, let the conductor ab move to the right in the same magnetic field at a faster speed. Observe the deflection angle of the sensitive galvanometer pointer.

C. By comparing the deflection angles of two sensitive galvanometers, we can know the relationship between the induced current and the velocity of the conductor.

(2) A; (3) the strength of the magnet and its moving speed; (4) Change the cutting direction (change the magnetic pole direction), change the magnetic pole direction (or change the moving direction of the magnet).