(20 1 1? Nantong) In the circuit shown in the figure, the power supply voltage is 6V, the fixed resistance R0 =10Ω, and the maximum resistance of the sliding rheostat R = 20Ω. ( 1).

(1) When the switch S is set to 1, the voltmeter measures the power supply voltage, so the indication is 6V.

(2) when the switch s is set to 2, R0 and r form a series circuit,

When the slider is at terminal A, I = UR0 = 6V10Ω = 0.6A, and the voltmeter indicates 6V.

When the slider is at terminal B, the total resistance in the circuit is RTotal =10Ω+20Ω = 30Ω.

Current in the circuit: I = Urtotal = 6V30Ω = 0.2A. 。

The voltage across R0: U0 = IR0 = 0.2a× 10ω= 2V, that is, the voltmeter indicates 2V.

(3) When the slider is at terminal A, the current in the circuit is the largest, and the voltage at both ends of R0 is the largest and the power is the largest.

P=UI=6V×0.6A=3.6W。

So the answer is: (1) When the switch S is set to contact 1, the voltmeter indicates 6V;

(2) When the switch S is set to contact 2, the minimum value of current representation is 0.2A；; The minimum value of voltmeter is 2V;

(3) The maximum power consumed by constant resistor R0 is 3.6W 。