(20 10? In the circuit shown in the figure, the supply voltage remains unchanged. Close the switch S, and when the slider P of the sliding rheostat moves to the right, the power supply is turned on.

When the slider P of the sliding rheostat moves to the right, the voltmeter V 1 always measures the voltage U 1 at both ends of R 1, and the ammeter measures the current I passing through R 1;

Therefore, according to Ohm's law, we can know that the resistance of U 1I=R 1 and R 1 remain unchanged, and the ratio of the indicated value of voltmeter V 1 to the indicated value of ammeter A remains unchanged.

Because that total voltage of the serie circuit is equal to the sum of the sub-voltages,

So U 1=U-U2, △U 1=△U2, that is, the change of voltmeter V 1 is equal to the change of voltmeter V2.

So, the answer is: unchanged; be equal to