"Measuring the resistance of a conductor according to Ohm's law" Ohm's law PPT courseware 7

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"Measuring the resistance of a conductor according to Ohm's law" Ohm's law PPT courseware 7

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Voltammetry uses a voltmeter to measure ______ at both ends of a conductor, uses an ammeter to measure ______ through the conductor, and then uses ______ to find the resistance of the conductor.

Experimental principle R=______

To be measured ______ across the resistor and ______ in the resistor

Measuring instruments voltmeter, ______, ______, power supply, switch, wire, etc.

1. Measure resistance by voltammetry

According to the deformation formula of Ohm's law R=?/?, by measuring the voltage at both ends of the resistance to be measured and the current passing through it, the resistance of the conductor can be found. This method is called voltammetry. Measuring resistance by voltammetry is an indirect measurement method, which requires not only mastering the knowledge of circuit connections, but also mastering the use of voltmeters, ammeters and sliding rheostat.

The resistance values ​​measured each time in the experiment are often different. If the difference is not big, this is normal. If the difference is large, it means there is an error in the measurement. In order to reduce the error, multiple measurements need to be made at different voltages and then averaged. The function of the sliding rheostat in the circuit is to change the voltage across the resistor to measure the current values ​​at different voltages.

2. Issues that should be paid attention to when measuring resistance by voltammetric method

(1) Designing the experimental circuit well and drawing the correct circuit diagram are the keys to the voltammetric resistance measurement experiment.

(2) When selecting experimental equipment, the specifications and performance of the equipment, the power supply voltage, the range of the ammeter and voltmeter, the resistance to be measured, and the maximum current allowed to pass through the sliding rheostat should be uniformly considered.

(3) According to the circuit diagram, correctly connecting the circuit is the basis for doing a good experiment. The following points should be noted when connecting the circuit:

a. During the process of connecting the circuit, switch S should always be in the off state;

b. The sliding blade of the sliding varistor R should be placed in a position where the resistance in the circuit connected to it is at the maximum value;

c. Select the range of the ammeter and voltmeter and identify their positive and negative terminals.

[Example] In the experiment of measuring resistance Rx by voltammetry, we use the circuit as shown in the figure to measure. The measurement result is expressed by dividing the voltmeter reading by the ammeter reading. As electrical appliances, voltmeters and ammeters have resistance, which will cause experimental errors.

(1) Before the power is turned on, the sliding blade of the sliding rheostat should be at ______ (optional "left end", "right end" or "any position");

(2) The measured value is ______ compared with the true value (optional "larger", "smaller" or "the same");

(3) If the readings of the voltmeter and ammeter are U and I respectively, and their own resistances are RV and RA respectively, then the more accurate expression of Rx is ______ (mathematical expressions are represented by known letters).

1. In the experiment of "voltammetric resistance measurement", if the power supply voltage is 3 V and the measured resistance is 20 Ω, the range of the voltmeter and ammeter should be selected ()

A.0~3 V, 0~3 A B.0~15 V, 0~3 A

C.0~3 V, 0~0.6 A D.0~15 V, 0~0.6 A

2. In the experiment of measuring resistance with ammeter and voltmeter, which of the following precautions is not necessary ()

A. Before connecting the circuit, turn off the switch

B. Connection should be started from the positive pole of the power supply, and the switch should be close to the positive pole of the power supply.

C. When the measured value cannot be estimated, the ammeter and voltmeter should use a larger range.

D. Do not connect the ammeter directly to the two poles of the power supply.

3. In the experiment of "voltammetric resistance measurement", the role that the sliding rheostat cannot play is ()

A.Change the current in the circuit

B. Change the resistance of the resistor being measured

C. Change the voltage across the resistor being measured

D. Protection circuit

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

"Measuring the resistance of a conductor according to Ohm's law" Ohm's law PPT courseware 6:

"Measuring the Resistance of a Conductor According to Ohm's Law" Ohm's Law PPT Courseware 6 Questions and Thoughts The teacher provided the students with several unmarked resistors, one of which is 12. Can you find out the resistance of this 12 through experiments? The experimental principle is based on Ohm's law..

"Measuring the resistance of a conductor according to Ohm's law" Ohm's law PPT courseware 5:

"Measuring the resistance of a conductor according to Ohm's law" Ohm's law PPT courseware 5 [Think about it] The content and mathematical expression of Ohm's law I=U/RR=U/I U is measured with a voltmeter (voltmeter) I Measuring with an ammeter (ammeter) [Go into the classroom] [Experiment name] Measuring the conductor...

"Measuring the resistance of a conductor according to Ohm's law" Ohm's law PPT courseware 4:

"Measuring the Resistance of a Conductor According to Ohm's Law" Ohm's Law PPT Courseware 4 There is a resistor with an unknown resistance in the laboratory. How to measure its resistance? Pass a current through the resistor, measure the current value and the voltage across the resistor, and apply Ohm's law to find Rx..

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Update Time: 2024-10-04

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