Xiaowen's experiment of measuring the rated power of the bulb marked "2.5V" shows that the resistance of the bulb used is about10Ω, and the maximum resistance of the sliding rheostat is 50Ω.

The rated voltage of (1) bulb is 2.5V, so the voltmeter should be in the range of 0 ~ 3V, and the current when the bulb normally emits light is about I = ur = 2.5v10Ω = 0.25a, so the ammeter should be in the range of 0 ~ 0.6A When the slider moves to the left, the lamp lights up, indicating that the connecting circuit slides when the slider moves to the left. The sliding rheostat is connected to the lower left terminal A, the ammeter, the bulb and the sliding rheostat are connected in series on the circuit, and the voltmeter is connected in parallel at both ends of the bulb. The circuit diagram is as follows:

(2) The functions of the sliding rheostat in this experiment are: 1. Protecting the circuit; The second is to adjust the voltage at both ends of the small bulb;

(3) By analyzing the data in the table, we can know that the actual power of the light bulb and the brightness of the light bulb are increasing gradually in the three experiments, so it can be concluded that the greater the actual power of the light bulb, the brighter the light bulb;

According to the experimental data in the table, the power corresponding to the rated voltage of the bulb is 0.60W, and the rated power of the bulb is 0.60 W;

(4) According to the equivalent replacement method, first switch on the switch S and A, adjust the rheostat slider to make the indicator of the voltmeter 2.5V, then switch on the switch S and B, keep the position of the sliding rheostat slider unchanged, and adjust the resistance box to make the indicator of the voltmeter 2.5V.,

Write down the resistance R0 of the resistance box connected to the circuit, which is the resistance of the small bulb when it normally emits light, and then the rated power of the bulb is P =(2.5v)2r 0.

So the answer is:

(1) circuit as shown;

(2) Adjust the voltage at both ends of the small bulb to make it equal to the rated voltage; (3)①0.6? (2) The greater the power of the bulb, the brighter the bulb; (4)a: Connect the switch to point A, and adjust the sliding rheostat to make the indication of the voltmeter equal to 2.5V；;

B: Change the switch to B, keep the position of the rheostat slider unchanged, and adjust the resistance of the resistance box until the voltage is still 2.5V At this time, record the resistance of the resistance box as R. 。

Expression P=(2.5V)2R0