"Measuring Resistance" Ohm's Law PPT Courseware

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"Measuring Resistance" Ohm's Law PPT Courseware

Want to discuss

1. Current can be measured with an ammeter, and voltage can be measured with a voltmeter. So, how to measure resistance?

2. How to use Ohm's law to find a way to indirectly measure the resistance of a conductor?

I =U/R R=U/I

1. Measure resistance by voltammetry

Experiment purpose: Use voltmeter and ammeter to measure resistance indirectly

Experimental principle R=U/I

Experimental equipment: power supply, voltmeter, ammeter, sliding rheostat, switch, wire, resistance to be measured.

1. Write out your 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.

Experimental steps

1. Adjust the pointers of the ammeter and voltmeter to zero scale; connect the physical objects according to the circuit diagram. Adjust the sliding rheostat to the maximum resistance end;

2. Close the switch, adjust the sliding blade of the sliding rheostat to the appropriate position, read the ammeter reading I and the voltmeter reading U respectively, and record them in the table;

3. Calculate the value of R according to the formula R=U/I and record it in the table.

4. Adjust the slider of the sliding rheostat to change the current in the resistance to be measured and the voltage at both ends, then measure several sets of data and calculate the value of R.

Precautions

1. Before connecting the circuit, adjust the ammeter and voltmeter to zero scale.

2. 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.

3. Connect the circuit, use the switch to test after checking that the circuit connection is correct, and then close the switch S after confirming that the circuit is intact.

4. Pay attention to selecting appropriate ranges for voltmeters and ammeters.

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.

3. Compare the calculated values ​​to see if the resistance values ​​calculated are the same each time? Is there any pattern of change?

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

2. Example analysis

Example 1 Xiaoying connects the experimental circuit according to the circuit diagram shown in Figure A and measures the resistance of the resistor R. After closing the switch S and adjusting the slider P of the sliding rheostat, observe that the indications of the voltmeter and ammeter are as shown in Figures B and C respectively. Then the indication of the ammeter is ____A and the resistance value of the resistor R is ____Ω.

Example 2 A classmate used voltammetry to measure the resistance of a small light bulb. The following table shows the recorded experimental data. What did you find? Explain the reason.

Analysis: The greater the voltage across the lamp, the greater the filament resistance.

Reason: When the voltage across the lamp becomes larger, the filament temperature increases.

Example 3 In the experiment of "Measuring the resistance of a small light bulb", a student accidentally connected the ammeter and voltmeter in the wrong position when connecting the circuit, as shown in the figure. Possible phenomena when closing the switch are ( )

A. The ammeter is burned out and the voltage indication is 0

B． Small light bulb burned out

C. The current representation number is 0, and the voltage representation number is the power supply voltage value.

D． The current representation number is 0, and the voltage representation number is 0

practice

1. Xiaodong is doing an experiment of "measuring the resistance of a small light bulb": (1) Please complete the connection of the experimental circuit as shown in the picture; (2) After Xiaodong correctly connects the circuit, close the switch and adjust the sliding rheostat so that the voltmeter reads as shown in the picture (A) ), at this time the ammeter indicates as shown in Figure (B), the resistance of the small light bulb is _____Ω.

2. Xiaodong did an experiment to measure the resistance of a light bulb. After connecting the circuit and closing the switch, he found that the light did not light up, the ammeter showed no reading, and the voltage indicated was the power supply voltage. What are the possible causes of the failure?

Please write down three reasons why the light bulb does not light up.

(1) The voltmeter is connected in series in the circuit;

(2) The small light bulb is broken;

(3) The wire or terminal connecting the two ends of the small bulb is broken.

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

"Measuring Resistance" Ohm's Law PPT Courseware 2:

"Measuring Resistance" Ohm's Law PPT Courseware 2 1. If a resistor does not have a resistance value marked, how to measure the resistance value? Experimental principle: Ohm's law I=U/R Deformation formula R=U/I 2. What are the physical quantities that need to be measured in the experiment? The electricity at both ends of the resistor...

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Update Time: 2024-10-04

This template belongs to Physics courseware Lu Jiao Edition Ninth Grade Physics Volume 1 industry PPT template

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