"Application of Ohm's Law" Exploring Ohm's Law PPT Courseware 3

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"Application of Ohm's Law" Exploring Ohm's Law PPT Courseware 3

1. Measure resistance by "voltammetry"

1. Principle: Ohm's law I=U/R deformation formula R=U/I

2. Equipment: power supply, switch, voltmeter, ammeter, sliding rheostat, small light bulb and some wires.

3. Experimental circuit diagram

2. Two kinds of short circuits

1. The whole circuit is short-circuited (power supply short-circuited).

2. Part of the circuit is short-circuited.

Two ways to measure resistance

Voltammetry

① Connect the circuit and place the sliding piece of the sliding rheostat at the maximum resistance point.

② Close the switch S, adjust the slider P to increase the current from small to large, and measure several sets of current values ​​and voltage values.

③ Calculate the voltage value of the filament under various lighting conditions. Be careful not to take the average value to calculate the resistance value of the small bulb.

alternative method

① Use an ammeter to measure the current I through the resistor Rx

② Replace the resistance box R′ and adjust the resistance so that the ammeter still reads I

③Then Rx＝R′

[Example]Use the instrument shown in Figure 12-3-2 to measure the resistance value of resistor R.

(1) Connect the circuit in Figure 12-3-2 into a correct measurement circuit

(2) The sliding rheostat in the circuit protects the circuit, so before the switch is closed, its slide should be moved to the extreme ____________ end (fill in "left" or "right"); during the experiment, the sliding rheostat has another One function is ____________.

(3) If the readings of the ammeter and voltmeter in the circuit are as shown in Figure 12-3-3, the reading of the ammeter is ____________ and the reading of the voltmeter is ____________.

Analysis: (1) The connection principle of the sliding rheostat is "one up, one down". The negative electrode of the power supply should be connected to any one of the two terminals of the resistance wire at the lower end of the sliding rheostat (here, we take the right terminal terminal of the resistance wire as an example); voltmeter measurement is the voltage at both ends of the resistor to be measured, and because the power supply is composed of two dry batteries connected in series, the voltmeter terminal "3" should be connected to the right end of the resistor to be measured, as shown in Figure 12-3-4;

(2) When connecting the circuit, in order to protect the circuit before closing the switch, the slider of the sliding varistor should be moved to the maximum resistance value. As shown in Figure 12-3-4, it should be moved to the far left;

(3) According to the selected range of the two meters and the deflection of the meter pointer, the current value and voltage value at this time can be read.

Class summary

1. When you want to measure the resistance of a certain conductor, you only need to use a voltmeter to measure the ________ at both ends of the conductor and use an ammeter to measure the ________ passing through it, and you can calculate it.

2. The two resistors are connected in the circuit respectively. It is known that U1:U2=3:2, R1:R2=1:2, then I1:I2=________.

3. In the experiment of "measurement of resistance by voltammetry", before connecting the circuit, first ________ switch. When the measured value cannot be estimated, the voltmeter and ammeter should use a larger ______ range.

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"Application of Ohm's Law" Exploring Ohm's Law PPT Courseware 2:

"Application of Ohm's Law" Exploring Ohm's Law PPT Courseware 2 Learning Objectives 1. Learn to measure resistance using voltammetry. 2. Be able to use Ohm's law to analyze practical problems such as the hazards of short circuits. 3. By using Ohm's law measurement and analysis and discussion, we know that the resistance of the filament varies with...

"Application of Ohm's Law" explores Ohm's Law PPT courseware:

"Application of Ohm's Law" Exploring Ohm's Law PPT Courseware Teaching Objectives. 1. Know how to measure resistance by voltammetry. 2. Be able to analyze the hazards of short circuit. 3. Be able to use Ohm's law to perform simple calculations. There is a resistor with an unknown resistance in the laboratory. How to measure its resistance? ..

"Application of Ohm's Law" Ohm's Law PPT courseware 5:

"Application of Ohm's Law" Ohm's Law PPT Courseware 5 Project Main content Indirect measurement of resistance The resistance of an unknown resistor can be measured by applying Ohm's law with the help of a resistor of known resistance under the condition of only a voltmeter (or only an ammeter). According to Ohm's law...

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Update Time: 2024-07-30

This template belongs to Physics courseware Guangdong and Shanghai Edition Ninth Grade Physics Volume 1 industry PPT template

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