(20 13? Heilongjiang) In the circuit shown in the figure, the power supply voltage is constant, and R 1 is a constant resistance. When the switch S is closed and the sliding vane of the sliding rheost

(20 13? Heilongjiang) In the circuit shown in the figure, the power supply voltage is constant, and R 1 is a constant resistance. When the switch S is closed and the sliding vane of the sliding rheostat moves to the left, 2 Solution: (1) When P moves to the left, the resistance of the sliding rheostat connected to the circuit becomes smaller.

The total resistance r of the circuit decreases and the power supply voltage u remains unchanged. It can be seen from I=UR that the circuit current increases and the current representation increases.

(2) According to the circuit diagram, the ammeter measures the circuit current, and the voltmeter measures the voltage across the resistor R 1 U 1.

According to ohm's law, r1= u1i. Since the resistance R 1 remains unchanged, the ratio of voltmeter to current indicator remains unchanged.

So, the answer is: bigger; there will be no changes.