(1) Connect the physical circuit diagram according to the principle of measuring electric power by voltammetry.

(2) Select the ammeter range according to the rated current of the bulb.

(3) Answer questions according to the formula of circuit and electric power.

Answer:

Solution:

(1) Voltammetry is used to measure the power of the bulb, ammeter is used to measure the current, and voltmeter is used to measure the voltage across the bulb. The circuit diagram is as follows:

(2) If the rated current of the bulb I=P/U=0.75W/2.5V=0.3A, the ammeter should be in the range of 0 ~ 0.6A;

(3) The resistance of the light bulb when it emits light normally: RL = U/I = 2.5V/0.3A≈8.3ω. When the resistance of the sliding rheostat is equal to the resistance of the light bulb, the power consumed by the sliding rheostat is the largest, and the maximum resistance of the sliding rheostat is15Ω. In the process of adjusting the resistance of the sliding rheostat from the maximum value to 5 Ω, the power consumed by the sliding rheostat first increases and then decreases.

So the answer is: (1) The circuit diagram is as shown in the figure; (2)0.6; (3) First get bigger and then get smaller.