"Measuring the Electric Power of Small Light Bulbs" Electric Power PPT Download

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"Measuring the Electric Power of Small Light Bulbs" Electric Power PPT Download

Reaching standards and consolidating

1. Multiple choice questions

1. The symbols "+" and "-" in Figure 3-K-1 represent the positive and negative terminals of the meter respectively. The circuit diagram that can measure the electrical power of the resistor R is ()

2. In the experiment of "Measuring the rated power of a small light bulb (known rated voltage) by voltammetry", which of the following statements is incorrect ()

A. When moving the sliding rheostat slide with your hand, your eyes should observe the indication of the voltmeter.

B. In the experiment, the function of the sliding rheostat is to change the rated power of the bulb under test

C. In the experiment, the function of the sliding rheostat is to change the voltage at both ends of the bulb under test and protect the circuit.

D. The rated power of the small light bulb refers to the power of the small light bulb when it normally emits light.

3. A student used the circuit shown in Figure 3-K-2 to measure the rated power of a small light bulb with a rated voltage of 2.5 V. Which of the following statements is incorrect ()

A. Before closing the switch, slide P should slide to end B

B. After closing the switch, the small light bulb does not light up, it must be

It's the filament of the small light bulb that's broken.

C. When the voltage indication is 2.5 V, the measured value is passed

The current of the small light bulb can be used to calculate the rated power of the small light bulb.

D. It can also be known from the experiment that the greater the actual power of the small bulb, the brighter the small bulb will be.

4. In the experiment of "Measuring the electric power of a small light bulb", it is known that the rated voltage of the small light bulb is 2.5 V. The data obtained by Xiuxiu through the correct experiment are as follows. The following conclusion obtained from the analysis of the data is correct ()

A. The resistance of the filament decreases as the voltage increases

B. The small light bulb has a rated power of 0.8 W

C. The rated power of the small light bulb is the average of the four times.

D. The current through the small bulb is proportional to the voltage across it

5. In the experimental skills test, the equipment prepared on the experimental table includes: student power supply, voltmeter, ammeter, sliding rheostat, switch, small light bulb to be tested and several wires. When doing the experiment of "measuring the electric power of a small light bulb", Xiao Ming accidentally reversed the positions of the two meters while connecting the circuit. The other connections were correct. When the switch was closed, the phenomenon that occurred was ()

A. The ammeter will be burned out

B. The voltmeter will be burned out

C. The voltmeter has a reading, but the ammeter’s reading is almost zero.

D. The ammeter has a reading, but the voltmeter has a reading of almost zero.

2. Fill in the blanks

6. Xiao Ming is doing an experiment of "measuring the electric power of a small light bulb". The light bulb used is marked with "2.5 V 3 W", then he should conduct at least ________ experiments with the purpose of measuring the voltage of the small light bulb at both ends ________ , ________ and ________ actual power at rated voltage and compare.

7. In the experiment of "measuring the electric power of small light bulbs", the power supply voltage selected should ________ (optional "greater than", "equal to" or "less than") the rated voltage of the small light bulb. The sliding rheostat should be in the circuit with the light bulb. Before closing the switch, the slider of the sliding rheostat should be placed at the position of maximum resistance. The purpose of this is to ________. Another function of the sliding rheostat is to _________.

3. Experimental research questions

8. When Xiaohua was doing the experiment of "measuring the electrical power of a small light bulb", he selected a small light bulb marked with "2.5 V" for the experiment, and made four consecutive measurements. The following table is the experimental data and results he obtained. observed phenomena.

Analyzing the data and phenomena in the above table, we can get:

(1) The rated power of the small light bulb is ________W.

(2) The experiment proves: under the rated voltage, the small light bulb can emit light normally; when the actual voltage is greater than the rated voltage, the actual power ________ the rated power, the small light bulb ________ (optional "brighter" or "darker") ; When the actual voltage is less than the rated voltage, the actual power ________ the rated power, and the small bulb ________ (optional "brighter" or "darker").

9. In the experiment of "Measuring the electric power of a small light bulb", the power supply voltage is 3 V, the rated voltage of the small light bulb is 2.5 V, and the resistance is about 10 Ω.

(1) The switch should ________ when connecting the circuit.

(2) Please use pen lines instead of wires to completely connect the physical circuit in Figure 3-K-3A.

(3) Before closing the switch, the slider P of the sliding rheostat should be at the ________ (optional "A" or "B") end.

(4) After Xiao Ming connected the circuit, he closed the switch and moved the slider. He found that the small light bulb always did not light up, and the voltmeter showed a reading but the ammeter did not. The cause of the fault may be ____________________. (Just write one)

(5) After troubleshooting, Xiao Ming closes the switch and moves the slide P to a certain position. The voltage indication (as shown in Figure B) is ______V, then the actual power of the bulb at this time is ________ (optional "greater than" "less than" or "equal to") rated power.

(6) Xiao Ming continues to move the sliding piece P of the sliding varistor, writes down the corresponding readings of multiple sets of voltmeters and ammeters, and draws it into an I-U image (as shown in Figure 3-K-4). According to the image , the rated power of the small light bulb can be calculated to be _______W.

(7) Further analysis of the image shows that as the voltage across the bulb increases, the filament resistance gradually ________ (select "increase", "decrease" or "unchanged"). The reason for this phenomenon may be ____________________________.

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Update Time: 2024-09-30

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