(1) Because the resistance is less than1Ω, and the maximum current in the circuit is 0.5 Ω, the maximum current is 0.5A, so we should choose V 1 to make the reading more accurate. Internal resistance r = ui = 0.5ω Ω Because the ammeter is used in the experiment, the current is too large, which leads to the measurement result is too small.

(2) The circuit uses a voltmeter to measure the voltage at both ends of the motor and an ammeter to measure the current, and the power is obtained by P=UI, so the relationship between the output power and the input voltage can be obtained; The answer is as follows:

(3) As can be seen from the figure, if the current I in the circuit is 0.40a, then the power consumed by the motor is P = UI = 4.5v× 0.3985a =1.80w; Power consumed on the internal resistance of the motor p1= i2r = 0.08w; Then the output power of the motor p =1.80-0.08w =1.72w. 。

So the answer is: (1)V 1, 0.5, small; (2) As shown in the figure; (3) 1.72.