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Use ammeter and voltmeter, measure the method of small bulb resistance to call voltammetry, what is the principle?
According to Ohm's law, r = u / I, the resistance of a conductor is equal to the ratio of the voltage at both ends of the conductor to the current passing through the conductor
Use a voltmeter and an ammeter to measure the voltage and current values respectively, and compare the resistance values
In the ammeter series a large resistance can become a voltmeter, in the ammeter parallel a small resistance can become an ammeter
It's best to give an example
The essence of ammeter and voltmeter is to add an appropriate voltage to the meter head to make it rotate, indicating the value of current and voltage
For example, for a meter, the full bias current (that is, the current required to deflect the pointer to the maximum scale) is 50ua, and the internal resistance of the meter is 2K. To change it to a 10V voltmeter, the total resistance of the voltmeter is 10V / 50ua = 200K, minus the internal resistance 2K of the meter itself, the resistance to be connected in series is 200-2 = 198k, that is to say, The meter connected in series with a 198k resistor can become a 10 range DC voltmeter
If you want to change this meter to a 1A DC ammeter, you can calculate as follows:
When the meter head is full biased, the current passing through the ammeter is 1a. Since the current passing through the meter head is 50ua, the current passing through the shunt resistor is 1a-50ua, which can be approximately 1a. The voltage at both ends of the ammeter is 50ua * 2K = 0.1V, so the shunt resistor to be paralleled should be 1A / 0.1V = 0.1 ohm
And so on for the rest
Sensitive ammeter how to refit into ammeter or voltmeter (how series, parallel resistance) some specific! Thank you~~
First of all, you should know that parallel connection is used for shunt, and series connection is used for partial pressure
Now suppose that the internal resistance of a sensitive ammeter is r
First of all, look at the ammeter. The ammeter is connected in series in the circuit, which is the same as the current of the component to be tested, but the current is often larger than the current that can be measured by the sensitive ammeter. At this time, it is necessary to make the large current not pass through the sensitive ammeter. How to do this is to connect the sensitive ammeter in parallel with a known resistance R1 whose resistance is much smaller than that of the sensitive ammeter, In this way, according to the current calculation of the parallel circuit, it can be calculated that most of the current will go through the branch with the small resistance, so as to ensure that the current passing through the sensitive ammeter is relatively small. At the same time, it can know the current flowing through the sensitive ammeter, assuming that it is I1, and then the total current can be calculated through the resistance of the sensitive ammeter and the resistance in parallel with it, That's the current we're going to test. [i = I1 * (R + R1) / R1]
Voltmeter, which is connected in parallel to the circuit, has the same voltage as the component to be measured. This voltage generally exceeds the maximum voltage of the sensitive ammeter. At this time, the voltage division function of the series circuit is used. The sensitive ammeter is connected in series with a known resistance R2 whose resistance value is much larger than that of the sensitive ammeter. In this way, the voltage of the sensitive ammeter can be reduced, At the same time, the current I2 flowing through the sensitive ammeter is measured. Through calculation, we can know the voltage U = I * r = I2 * (R + R2)
How to calculate the resistance value of voltmeter refitted from ammeter
Setting: the internal resistance of the meter is R0, the full-scale current is I. the range of the voltmeter is u. The resistance in series is r
The value of series resistance R can be obtained from the formula u = I * (R0 + R): r = u / i-r0
Different series resistance values can be obtained with different voltage ranges
RELATED INFORMATIONS
- 1. In the experiment of studying the relationship between current, voltage and resistance, the purpose of using sliding rheostat in the circuit is two times
- 2. On the physical experiment to explore the relationship between resistance and current in the circuit In order to keep the voltage at both ends of the conductor unchanged, it is necessary to adjust the sliding rheostat to a larger value when replacing a larger constant value resistor in the experiment. Why and why?
- 3. All formulas and experiments, such as voltammetric resistance measurement For example: w = FS Important experiments. Voltammetric resistance and so on. Now
- 4. The principle of the experiment of measuring resistance by voltammetry is as follows______ In the process of connecting the circuit, the switch must be in the______ The slide of the sliding rheostat should be at the lowest resistance______ The main purpose of this is to avoid the interference in the circuit______ &After the power is turned on, first adjust the voltage at both ends of the small bulb to zero through the sliding rheostat______ For the safety of the equipment, the measurement should start from the rated voltage step by step______ Voltage, (fill in "up" or "down") to obtain several sets of data
- 5. What is the experimental principle applied in the experiment of measuring resistance by voltammetry?
- 6. When doing the experiment of measuring resistance by volt ampere method, the connection circuit is as shown in the figure. Please think about the following troubleshooting methods: (1) if the pointer of ammeter reverses after the switch is closed, this is because______ We can use it______ (2) if the voltmeter shows the number after the switch is closed and is close to the voltage value of the power supply, and the pointer of the ammeter hardly moves, this is because______ (3) if the ammeter shows the number after the switch is closed, the voltmeter does not______ (4) if the current indication is large after the switch is closed, it is because______ (5) if the current indication is very small after the switch is closed, adjust the slide of the sliding rheostat, and the pointer does not move because______ (6) (it can be seen from the experimental data) when the slide plate of the sliding rheostat is moved in the experiment, the indication of the two meters increases or decreases at the same time. If the opposite situation occurs, it is because______ ．
- 7. How to do the experiment of measuring resistance by voltammetry? If the control resistance does not change, why does it slide the slide to change the resistance? If the control voltage does not change, why does the voltmeter display different every time I'm going crazy What can t t do? It's too hard. I can't do it at all
- 8. Experimental principle and steps of measuring nonlinear resistance by voltammetry ditto Who will design a circuit diagram for measuring nonlinear resistance by volt ampere method Mainly the experimental principle, experimental steps!
- 9. There is an ammeter g with internal resistance Rg = 25 Ω and full bias current Ig = 3mA. How much resistance should be paralleled to refit it into an ammeter with a range of 0-0.6ma What is the internal resistance of the modified ammeter?
- 10. In the circuit shown in the figure, the power supply voltage is 3V, the resistance R1 is 10ohm, and the resistance is 5ohm. After the switch is closed, what is the connection mode between R1 and R2
- 11. For the existing power supply with unknown voltage [voltage unchanged], one ammeter, one voltmeter, one sliding rheostat [known maximum resistance is R0] and one resistance Rx to be measured, There are two switches and several wires. Please draw two different schemes of measuring RX resistance according to the requirements, and write down the experimental steps and the process and expression of calculating Rx
- 12. When the switch is closed for the experiment, it is found that the voltmeter and ammeter show the number no matter how the slide rheostat is moved. What is the reason In the experiment of measuring constant resistance or measuring electric power of small bulb
- 13. In the circuit as shown in the figure, the power supply voltage does not change. When s is closed and the slide P of the sliding rheostat moves from left to right, the change of the indication of the three meters is () A. A bigger, V1 unchanged, V2 bigger B. a bigger, V1 smaller, V2 unchanged C. A unchanged, V1 smaller, V2 bigger D. a smaller, V1 bigger, V2 bigger
- 14. As shown in the figure, when the power supply voltage remains unchanged and the switch S is closed, when the slide P of the sliding rheostat moves from left to right, the change of the three meters is () A. V1 increases, V2 decreases, a increases, B. V1 decreases, V2 increases, a decreases, C. V1 remains unchanged, V2 increases, a remains unchanged, D. V1 remains unchanged, V2 decreases, a remains unchanged
- 15. R is the resistance box, V is the ideal voltmeter, when the resistance box is R1 = 2 ohm, the voltmeter reading is U1 = 4V, when the number of resistance boxes is R2 = 5 ohm, the number of voltmeters is U2 R is the resistance box, V is the ideal voltmeter. When the resistance box is R1 = 2 ohm, the reading of the voltmeter is U1 = 4V. When the number of resistance boxes is R2 = 5 ohm, the number of voltmeters is U2 = 5V
- 16. As shown in the figure, R1 = 6 Ω, the reading of ammeter A1 is 0.5A, and the degree of ammeter A2 is 0.3A? (2) What is the resistance of R2?
- 17. If two resistors R1 and R2 are connected to a 3V power supply, calculate the indication of the ammeter, and calculate the electric energy consumed when the 30s resistance is 3V
- 18. A series circuit ammeter calculates the current representation between two resistors
- 19. In the circuit shown in the figure, the voltage U remains unchanged, the resistance R1 = R2, when the switch S is open, the indication of the ammeter is I1; when the switch S is closed, the indication of the ammeter is I2, then I1: I2=______ ．
- 20. As the circuit shown in the figure, the power supply voltage is 12V, the resistance value of R1 is 10 Ω, the number of a meter and A1 is 1a and 0.4A respectively, then what is the resistance value of R2?