The voltmeter is connected in series with a resistor. Whose voltage is the measured voltage?

The voltmeter is connected in series with a resistor. Whose voltage is the measured voltage?

The resistance of the voltmeter is very large. When it is connected in series with the resistor, it measures the voltage distributed on the resistance of the voltmeter. If the resistance on the resistor is very small, it is about the voltage of the power supply

The law of series, parallel, circuit, current, voltage and resistance

1. I = u / R (Ohm's Law: the current in a conductor is directly proportional to the voltage at both ends of the conductor and inversely proportional to the resistance of the conductor)
2． I=I1=I2=… =In (characteristic of current in series circuit: current is equal everywhere)
3． U=U1+U2+… +UN (characteristics of voltage in series circuit: in series circuit, the total voltage is equal to the sum of voltage at both ends of each circuit)
4． I=I1+I2+… +In (the characteristic of current in parallel circuit: the current on the main circuit is equal to the sum of the currents in each branch circuit)
5． U=U1=U2=… =UN (characteristics of voltage in parallel circuit: the voltage at both ends of each branch is equal to the power supply voltage)
6． R=R1+R2+… +RN (characteristic of resistance in series circuit: the total resistance is equal to the sum of resistance of each part of the circuit)
7． 1/R=1/R1+1/R2+… +1 / RN (the characteristic of resistance in parallel circuit: the reciprocal of total resistance is equal to the sum of the reciprocal of each parallel resistance)
8. R and = R / n
9. R series = NR (formula for calculating total resistance when n identical resistors are in series)
10. U1: U2 = R1: R2 (relationship between voltage and resistance in series circuit: the ratio of voltage is equal to the ratio of their corresponding resistance)
11. I1: I2 = R2: R1 (relationship between current and resistance in parallel circuit: the ratio of current is equal to the inverse ratio of their corresponding resistance)

Now there are two identical pencils, a coil of fine copper wire with a known diameter of 1 mm. Please try to find out the diameter of another coil of fine iron wire

Use this roll of thin copper wire with known diameter to wrap it on the pencil evenly and compactly (wrap it up, cut off if there is surplus). Wrap another roll of copper wire on another pencil (wrap it up, cut off if there is surplus). Count the number of turns N1 of copper wire with known diameter and the number of turns N2 of copper wire wrapped on another pencil. Use 1 mm times turns N1 to calculate the length s of pencil, and then divide s by turns N2 of another roll

There are only two pencils with the same diameter. One coil of copper wire is known to be 1 mm in diameter. Please try to measure the diameter D of the other coil

Let the diameter of the thin wire to be measured be D, the number of turns n ', and the number of turns of the copper wire with a diameter of 1 mm be n. because the total width of the winding is the same, that is, n × 1 mm = n ′× D, the diameter of the thin wire is d = NN ′× 1 mm = NN ′ mm