Chenzhou property intelligent electric meter installation

As can be seen from the figure, the sliding rheostat is connected in series with the bulb, the voltmeter measures the voltage at both ends of the bulb, and the ammeter measures the current in the whole circuit.

When the slider P of the sliding rheostat slides to the right, the resistance of the sliding rheostat becomes larger,

According to the characteristics of resistance in series circuit, the total resistance in the circuit becomes larger;

The total voltage of the circuit is equal to the power supply voltage and remains unchanged.

According to ohm's law I=UR, the current in the circuit becomes smaller, that is, the pointer of the ammeter becomes smaller;

However, the resistance of the bulb remains the same. According to the formula U=IR, the voltage at both ends of the bulb becomes smaller, that is, the voltage representation number becomes smaller;

The current in the circuit becomes smaller and the resistance of the bulb remains the same.

From the formula P=I2R, we can see that the actual power of the light bulb becomes smaller, so the brightness of the light bulb becomes dim.

So choose C.