(1) After the positive and negative poles of the power supply are switched, the current direction in the conductor changes, and the moving direction of the conductor ab changes, which shows that the force direction of the charged conductor is related to the current direction.

The charged conductor is forced to move in the magnetic field, and electric energy is converted into mechanical energy; On this basis, an engine was manufactured.

(2) Connect the ammeter with the bulb in series and the voltmeter in parallel, as shown:

The current is 0.24A, so the ammeter can choose the range of 0 ~ 0.6a, and the dividing value is 0.02A The pointer position is as follows:

Secondary resistance R = UI = 2V0.24A = 8.3Ω.

Draw points according to the data in the table and connect them with smooth curves, as shown in the figure:

The brightness of a small light bulb depends on its actual electric power;

If the small bulb is replaced by an electromagnet, if more nails are attracted, the resistance of the sliding rheostat will be reduced, and the slider P will move to the left, which will increase the current in the circuit.

So the answer is:

(1) current; Machinery; Motor; (2) See the above diagram for circuit connection, image and current representation; 8.3; Actual power; To the left