"Measuring the Electric Power of Small Light Bulbs" Electric Power PPT Teaching Courseware

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"Measuring the Electric Power of Small Light Bulbs" Electric Power PPT Teaching Courseware

Part One: Knowledge Management

Measure the electrical power of a small light bulb

Principle: P=UI.

Equipment: battery pack, voltmeter______, ammeter______, sliding rheostat, switch and wires, small light bulb (marked with 2.5 V).

Steps: (1) Connect the circuit as shown in the figure, place the sliding plate of the sliding rheostat at the position with the largest resistance, close the switch, adjust the sliding plate of the sliding rheostat so that the voltmeter indicates U = 2.5 V, and record it at the same time. The indication I of the lower ammeter;

(2) Calculate the rated power P = UI of the small light bulb;

(3) Adjust the sliding rheostat so that the voltage at both ends of the small bulb is slightly higher or slightly lower than the rated voltage, measure the corresponding current value, and find the actual power of the small bulb not at the rated voltage.

Conclusion: The luminescence of the small light bulb is determined by the actual power. The greater the power, the brighter the light bulb. When the actual voltage across the bulb is equal to the rated voltage, the bulb lights normally; when the voltage is lower than the rated voltage, the bulb glows darker than normal; when the voltage is higher than the rated voltage, the bulb glows brighter than normal.

Note: In the experiment of measuring the electric power of a small light bulb, three sets of data were measured, and three electric powers of different sizes were obtained. However, these three electric powers are the electric powers in different states, and the average value cannot be calculated as the final result. This is meaningless.

(1) Observe the measuring ranges of the ammeter, voltmeter, sliding rheostat and the maximum current allowed to pass through. When selecting the measuring range, the measuring range of the voltmeter should be greater than the rated voltage of the small light bulb, and the measuring range of the ammeter should be greater than the rated current of the small light bulb. The resistance of the sliding rheostat should preferably be comparable to that of a small light bulb.

(2) When connecting the physical circuit according to the circuit diagram, the switch must be turned off.

(3) Before closing the switch, the slider of the sliding rheostat should be placed at the maximum resistance value so that the resistance in the circuit is maximized.

Measuring the electrical power of small light bulbs PPT, part 2: classification and exploration

One type: Voltammetry measures the electrical power of small light bulbs

[2018•Shandong Dezhou]In the experiment of measuring the electric power of the small light bulb, the power supply voltage was 4.5 V, the rated voltage of the small light bulb was 2.5 V, and the resistance of the small light bulb when it emitted light normally was about 10 Ω.

(1) Connect the physical circuit in Figure A completely. Requirements: When the sliding blade of the sliding rheostat moves toward terminal A, the resistance connected to the circuit becomes larger, and the connections must not cross.

(2) When Xiaogang closes the switch and moves the slider P to a certain position, the voltage indication (as shown in Figure B) is 2.2 V. If he wants to measure the rated power of the small light bulb, he should change the sliding rheostat in Figure A The slider P moves toward end B (optional "A" or "B"). The I-U image in Figure C was drawn by Xiaogang based on multiple sets of experimental data. According to the image, the rated power of the small light bulb can be obtained as 0.5W.

(3) From the I-U image in the experiment, it was found that the resistance of the small bulb changes, and the main factor affecting its change is temperature.

(4) If you replace the small light bulb with a fixed-value resistor, you can also explore the relationship between B (optional "A" or "B").

A． Current and resistanceB. Current and voltage

Type 2: Measuring electrical power using special methods

[2017•Guangzhou, Guangdong]A household incandescent lamp is marked "220 V? W", and the rated power value is unclear. Xiao Ming thought of using the household electric energy meter as shown in the picture. The dial is marked "3 200 imp/(kW·h)", which means that for every 1 kW·h of electricity consumed, the indicator light flashes 3 200 times. ; Its rated power can also be measured.

(1)The maximum current allowed by this electric energy meter is 40 A.

(2) In order to complete the experiment, one piece of equipment that needs to be supplemented is a stopwatch.

(3) Please design an experimental plan for measuring the electric power of the light bulb, and write down reasonable experimental steps and final expressions.

[Method Summary] To answer such questions, we must first understand the physical meaning of "3 200 imp/(kW·h)": when an electrical appliance consumes 1 kW·h of electric energy, the indicator light of the electric energy meter flashes 3,200 times.

Measuring the electrical power of small light bulbs PPT, part three: evaluation in class

1. [2019•Shandong Linyi]In the experiment of "Measuring the electrical power of a small light bulb", the reasonable division of labor between the hands and eyes during operation is: the hand moves the sliding plate of the sliding rheostat, and the eyes observe (A)

A． The indication of the voltmeter B. ammeter indication

C. Is the light bulb glowing? D. Rheostat slider position

2. [2018•Heilongjiang Harbin]Xiao Ming measured the power of the small light bulb according to the circuit as shown in the figure. The equipment specifications are as follows: the power supply voltage is always 6 V, the rated voltage of the small light bulb is 2.5 V, and the filament glows normally when the light bulb The resistance is about 10 Ω, the specifications of rheostat A are "10 Ω | 1 A", the specifications of rheostat B are "50 Ω | 0.5 A", ammeter (0～0.6 A, 0～3 A), voltmeter (0～3 V, 0～15 V), which of the following statements is wrong (B)

A． When connecting the experimental circuit, the sliding varistor slider should be placed at the far right end

B． The varistor should be selected as "10 Ω 1 A"

C. It can be found from experiments that the actual power and brightness of light bulbs are different under different voltages.

D. When measuring electrical power at different voltages, in order to reduce errors, a voltmeter with a range of 0 to 3 V should be used.

3. [2018 • Changsha, Hunan Province Multiple sets of data, and based on the ammeter and voltage indication numbers, the I-U image as shown in Figure B is created. It is known that the rated voltage of the small light bulb is 2.5 V and the power supply voltage is 4.5 V. The power of the small light bulb when it normally emits light is 0.5 W. If the maximum allowable voltage across the small bulb is 3 V, then the minimum value of the sliding rheostat connected to the circuit is 6.82 Ω. At this time, the actual power of the small bulb is 0.66 W. (If the result is a decimal, keep two decimal places)

4. [2018•Beijing]Xiaoyang connected the circuit as shown in the figure in order to measure the electric power of a small light bulb with a rated voltage of 2.5 V at different voltages and to observe the light emission of the small light bulb.

(1) Before closing the switch, the slider P of the sliding rheostat should be placed at the right (optional "left" or "right") end.

(2) Xiaoyang’s experimental records are shown in the table below. When the voltage across the small bulb is U=1.3 V, the electric power P=0.26 W.

(3) From the experimental records in the above table, you can also draw the conclusion: the greater the voltage of the lamp, the greater the resistance of the lamp. (Just write one)

(4) Experiments that can be performed using the experimental circuit as shown in the figure include: measuring the resistance of the light bulb. (Just write one)

Measuring the electrical power of small light bulbs PPT, Part 4: Layered operations

1. [2018•Anhui Huaibei]When doing the experiment of "voltammetric method to determine the electric power of small light bulbs", a classmate designed four experimental circuit diagrams, among which the correct one is (D)

2. [2019•Shandong Linyi]A classmate used an electric energy meter to measure the electric power of an electric water heater at home. The meter was marked with "600 r/(kW·h)". After turning off other electrical appliances at home, let The water heater works for 1 minute and the dial rotates 20 times. Which of the following statements is correct (C)

A． The electric power of the water heater is 1 000 W

B． The electric power of the water heater is 1 500 W

C. The electric power of the water heater is 2 000 W

D. The electric power of the water heater is 2 200 W

3. [2018•Xiamen, Fujian] Xiaolin designed four circuits as shown in the figure to measure the rated power of the small light bulb (the rated voltage of the small light bulb and the resistance of the fixed value resistor R0 are known), where The circuit that can accomplish the purpose of measurement is (A)

4. As shown in Figure 1, during the experiment of "measuring the electric power of a small light bulb", a classmate mistakenly connected a voltmeter in parallel to both ends of the sliding rheostat. He started recording the first set of data when the slider was placed at the far right end, and adjusted the slider to measure the electric power of a small light bulb. With multiple sets of data, the drawn U-I image is shown in Figure 2. It is known that the rated voltage of the small light bulb is 2.5 V and the power supply voltage is 4.5 V. The resistance value of the small light bulb when it emits light normally is 12.5 Ω. , the rated power is 0.5 W, and the maximum resistance of the rheostat is 40 Ω. In order to ensure that the voltage at both ends of the small light bulb does not exceed 3 V in the experiment, the minimum resistance of the sliding rheostat connected to the circuit is 6.8 Ω (retaining one decimal place).

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Update Time: 2024-07-03

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