Explore the experiment (1) given a power supply, a voltmeter, a constant resistance (known its resistance), a number of switches and wires, try to design a circuit diagram It can measure the resistance of an unknown resistance according to certain steps You want to draw a picture for me~ In addition, the corresponding letters should be used to represent the physical quantities measured by the elder brother Represents each measured physical quantity Can you give me a picture

Explore the experiment (1) given a power supply, a voltmeter, a constant resistance (known its resistance), a number of switches and wires, try to design a circuit diagram It can measure the resistance of an unknown resistance according to certain steps You want to draw a picture for me~ In addition, the corresponding letters should be used to represent the physical quantities measured by the elder brother Represents each measured physical quantity Can you give me a picture

1. Do not connect the unknown resistance first, connect normally, and measure the power supply voltage v
2. Connect all of them in series, and connect the voltmeter to the constant resistance. At this time, the current can be obtained according to I = U1 / R, then the voltage of unknown resistance U2 = v-u1, and then the unknown resistance can be obtained according to resistance = voltage / current, that is, RX = U2 / I!

At present, there are voltmeter, battery pack, known resistance value, fixed resistance R0, switch and several wires. It is required to measure the resistance value of Rx, write out the steps and draw the circuit

If the resistance values of R0 and Rx are not very large (far less than the internal resistance of voltmeter), the following methods can be used:
After connecting R0 and Rx in series, connect them to both ends of the battery pack through the switch, connect the voltmeter to both ends of R0 and Rx in turn, and the measured readings are U0 and UX respectively, then R0: RX = U0: UX, and Rx = R0 * UX / U0 can be obtained
The circuit diagram will not be drawn, and the previous text should be able to understand

The method for measuring the maximum resistance value RX of sliding rheostat, existing equipment: a constant resistance, power supply with unknown voltage, a voltmeter, a switch, several wires
1. Draw the circuit diagram 2. Briefly describe the physical quantity to be measured in the process of the experiment, and use the corresponding letters to represent 3. Use the known measured value to represent Rx

1. The sliding rheostat, setting resistance R, power supply and switch are connected in series with wires, and then the voltmeter and setting resistance R are connected in parallel. 2. Adjust the value of sliding rheostat in the circuit to 0, and then the voltage is expressed as power supply voltage U. adjust the value of sliding rheostat in the circuit to the maximum Rx, and then the voltage is expressed as u1.3, electricity

Li Qiang found that the voltmeter was damaged when he did the experiment of measuring resistance and Rx resistance, so he redesigned a circuit, chose a R1 with known resistance, and connected the circuit as shown in the figure. He first connected the wire C terminal to the "-" terminal of the ammeter, and the reading of the ammeter was I1, then connected the wire C terminal to the "3" terminal of the ammeter, and the reading of the ammeter was I2, then the resistance of Rx was I2______ (in known letters)

Connect the wire C to the "3" terminal of the ammeter, R1 and Rx are connected in parallel. At this time, the ammeter measures the current I2 passing through R1, and the voltage at both ends of the setting resistance R1 is U1 = i2r1. Because of the parallel circuit, it is the power supply voltage u = U1 = i2r1. Connect the wire C to the "- terminal of the ammeter, and R1 and Rx are connected in parallel. At this time, the ammeter measures the total current I1 of the trunk circuit, and according to the characteristics of the current in the parallel circuit, it is obtained that the current of the trunk circuit passes through Rx So the expression of resistance Rx is: RX = UXIX = uix = i2r1i1 − & nbsp; I2. So the answer is: i2r1i1 − & nbsp; I2