"Measurement of Resistance" Ohm's Law PPT Courseware 2

Description

"Measurement of Resistance" Ohm's Law PPT Courseware 2

Want to discuss

What basic physical quantities have we learned about electricity so far? How are these physical quantities measured?

From Ohm's law I=U/R, it can be deduced that R=U/I

It can be seen that the resistance of a conductor is indirectly measured by measuring current and voltage. This method is called "voltammetry" to measure resistance.

1. Experiment: Measure resistance by voltammetry

design experiment

In order to reduce the error, the voltage at both ends of the resistance to be measured should be changed during the experimental measurement, the voltage and current values ​​should be measured multiple times, the resistance should be calculated based on each voltage and current value, and finally the average value of the resistance should be calculated.

Experimental requirements

1. Write out experimental procedures and experimental data recording forms;

2. Connect the circuit according to the circuit diagram and make measurements;

3. Record the measured data in a record sheet designed by you;

4. Based on the measured data, calculate the resistance value using Ohm's law;

5. Measure several sets of data to see if the measured resistance values ​​are the same.

Precautions

1. When connecting the circuit, the switch should be turned off. After connecting the circuit, the sliding rheostat should be adjusted to the maximum resistance end.

2. Connect the circuit. After checking that the circuit connection is correct, test the switch with the switch. Make sure that the circuit is intact before closing the switch.

3. For voltmeters and ammeters, pay attention to selecting the appropriate range and the "+" and "-" connections.

4. When recording data, the switch should be turned off in time.

5. When arranging equipment, you should first turn off the switch and remove it from both poles of the power supply.

2. Experiment: Measure the resistance of small light bulbs by voltammetry

Think about it, do it

1. Replace the fixed-value resistor in the above experiment with a small light bulb and use the same method to measure the resistance of the small light bulb.

2. Measure several sets of data and calculate the resistance of the small light bulb based on the experimental data. Compare the calculated values ​​to see if the calculated resistance is the same each time. Is there any pattern of change?

3. If the situation that occurs is different from when measuring a fixed value resistance, how do you explain it? Talk to your classmates.

Analysis and Demonstration

Phenomenon: The resistance of the small light bulb increases as the voltage increases.

Reason: The higher the voltage across the small bulb, the brighter the lamp, and the higher the filament temperature. The resistance of the metal increases as the temperature increases, so the filament resistance will change with the brightness.

Conclusion: The resistance of a small light bulb changes with temperature (brightness).

Note: It is inappropriate to average the resistance values ​​measured at different temperatures.

Class exercises

1. When measuring resistance with a voltmeter and ammeter, the basis is _____; if the voltmeter and current are known as shown in the figure, the voltmeter reading is _____, the ammeter reading is _ ___, and the measured resistance is __ ___ .

2. A small light bulb with a rated voltage of 3.8V. Xiao Ming measured its resistance at 1.2V, and then adjusted the voltage across the bulb to 3.8V to measure its resistance. Xiao Ming found that the resistance at the last time was much greater than the first time. ,This is because( )

A. The experimental method is wrong

B． Experimental error

C. The resistance of a conductor is related to temperature

D. experimental error

3. A 20Ω resistor is connected to a power supply consisting of 4 dry batteries connected in series. To measure the current in this resistor and the voltage at both ends, the selected range of the ammeter and voltmeter should be ( )

A. 0～0.6A, 0～3V

B． 0～0.6A, 0～15V

C. 0~3 A, 0~3 V

D. 0~3 A, 0~15 V

4. After a student connected the experimental equipment with the circuit shown in the figure, he closed the switch. The light bulb glowed normally, but the voltmeter pointer did not move. This may be ()

A. The ammeter is burned out and the circuit is open

B． The ammeter is intact, but the wire connected to the ammeter is broken.

C. Short circuit in the wire at the voltmeter terminal

D. Wire break at voltmeter terminal

Keywords: Ohm's law teaching courseware, resistance measurement teaching courseware, New People's Education Edition ninth grade physics PPT courseware, ninth grade physics slide courseware download, Ohm's law PPT courseware download, resistance measurement PPT courseware download, .ppt Format

For more information about the "Ohm's Law Measurement of Resistance" PPT courseware, please click the Ohm's Law ppt Measurement of Resistance ppt tag.

"Measurement of Resistance" Ohm's Law PPT courseware 5:

"Measurement of Resistance" Ohm's Law PPT Courseware 5 Think about the following questions: 1. Can you design a circuit that can be used to measure resistance? Please draw the circuit diagram. 2. What is the experimental principle you envision? 1. Measure resistance by voltammetry 1. Experimental principle: R=U/I 2...

"Measurement of Resistance" Ohm's Law PPT courseware 4:

"Measurement of Resistance" Ohm's Law PPT Courseware 4 Learning Objectives 1. Further master the method of using voltmeters and ammeters 2. Learn to use voltammetry to measure resistance 3. Deepen the understanding of Ohm's law and its application Think about how to use Ohm The law is found to indirectly measure conductors..

"Measurement of Resistance" Ohm's Law PPT courseware 3:

"Measurement of Resistance" Ohm's Law PPT Courseware 3 Review the past and learn the new 1. The voltmeter connected in parallel at both ends of the wire shows: 2. The voltmeter connected in series in the circuit shows: 1. Three basic physical quantities of the circuit: Physical quantity: current I, Measuring Tool: Ammeter (Ammeter)..

File Info

Update Time: 2024-11-09

This template belongs to Physics courseware People's Education Edition Ninth Grade Physics Complete Book industry PPT template

Preview