The power supply voltage of the series circuit remains unchanged, and there is a constant resistance R in series in the circuit. In order to slightly increase the indication of the ammeter, it is necessary to give R--- The answer is to parallel a resistor much larger than R. but what is the reason?

The power supply voltage of the series circuit remains unchanged, and there is a constant resistance R in series in the circuit. In order to slightly increase the indication of the ammeter, it is necessary to give R--- The answer is to parallel a resistor much larger than R. but what is the reason?

According to the formula of parallel resistance:
1/R＝1/R1+1/R2
When R2 is large, 1 / r2 will be very small, then 1 / R will only increase by a small amount, and its reciprocal r will only decrease by a small amount
It is not suitable to use the formula r = R 1 * r 2 / (R 1 + R 2) to judge this change, because it is not easy to analyze. It is easy to judge by using the reciprocal 1 / R