"Improving Core Competencies in This Chapter" Electric Power PPT

"Improving Core Competencies in This Chapter" Electric Power PPT

Part One: Key Breakthroughs

1. An important measurement tool - electric energy meter

(1) Purpose: Measure the ________ consumed in the circuit.

(2) Connection method: ________ is connected in the household circuit.

(3)Unit: ________.

(4) Nameplate data meaning: “220 V” on the electric energy meter represents ____________________________; “10 A” in “10(20)A” represents ____________________, and “20 A” represents ____________________; “600 r/(kW· h)” means _______________________________________________; “50 Hz” means ____________________________.

2. Three important physical quantities

1. Electrical energy (electrical work): When electric current passes through an electrical appliance, the electric energy is converted into _______________, and at this time the current _________. That is, the process of current doing work is the process of converting ________ into ____________. The unit of electrical energy is ________, and the symbol is ________. The commonly used units are ________, and the symbol is ________. The conversion relationship between them is __________________.

2. Electric power: Electric power is a physical quantity that represents the electrical energy consumed by electrical appliances. It is the electrical work done by the current within a certain period of time and ____________________. The unit of electrical power is ________, and the symbol is ______; the electrical power of a certain electrical appliance is 1000 W, and its physical meaning is ____________________________. The calculation formulas for electric power include ________ and ________ (common formula).

3. Electric heating: The heat generated when an electric current passes through a conductor is _________ proportional to the square of the current, _________ to the resistance of the conductor, and _________ to the energization time. Its expression is ____________.

3. Common calculation formulas for three physical quantities

1. Four calculation formulas for electrical energy or electrical work

W=________=________=________=________; where the formulas __________ and ________ are only applicable to purely resistive circuits.

2. Four calculation formulas for electric power

P=________=________=________=________; where the formulas ________ and ________ are only applicable to purely resistive circuits.

3. In a purely resistive circuit, four calculation formulas for electric heating

Q=W=________=________=________=________.

4. Two important experiments

1. Voltammetry to measure the electrical power of small light bulbs

(1) Experimental principle: ________.

(2) Experimental equipment: power supply, wires, ammeter, ________, switch, small light bulb, ____________.

(3) Experimental circuit (drawn in the dotted box):

(4) The functions of the sliding rheostat: first, to protect the circuit, and second, to _______________.

(5) Experimental process: ① Connect the physical diagram according to the circuit diagram and connect the sliding rheostat to the circuit with the maximum resistance; ② Close the switch, move the slider of the sliding rheostat so that the voltage at both ends of the small bulb is the rated voltage, and read the ammeter at this time Display the number, use the formula __________ to calculate the rated power of the small bulb, and observe the brightness of the small bulb; ③ Move the slider of the sliding rheostat so that the actual voltage at both ends of the small bulb is slightly greater than the rated voltage and less than the rated voltage, and record the corresponding Calculate the corresponding actual power based on the ammeter's indication, and observe the brightness of the small bulb in the two situations.

(6) Experimental conclusion: The greater the actual power of the small light bulb, the ________ of the small light bulb.

(7) Precautions: ① During the experiment, while moving the slide of the sliding rheostat by hand, observe the display of the voltmeter with your eyes; ② When adjusting the voltage at both ends of the small bulb to be higher than the rated voltage, be careful to slowly adjust the slide of the sliding rheostat. The voltage cannot exceed 1.2 times the rated voltage, and the power-on time cannot be too long, otherwise the small bulb will easily burn out.

2. Explore the relationship between heat generated by conductors, current, and resistance

(1) Experimental device and operation: As shown in Figure 18-T-1A, the purpose of connecting the 5 Ω resistor a and the 10 Ω resistor b in series in the experiment is to control the ________ through the conductor and the energized ________ to be equal , this method of studying the problem is ______________; in Figure B, a 5 Ω resistor is connected to the outside of the container on the right, and its function is ____________________. In the experiment, the amount of heat generated by the current passing through the resistor is reflected by observing ____________________________. This method is called the "conversion method".

(2) Experimental conclusion: When the current and energization time are the same, the greater the resistance, the heat generated by this resistor is ________; when the resistance and energization time are the same, the greater the current passing through a resistor, the heat generated by this resistor Heat ________.

This chapter’s core literacy improvement PPT, part two: scientific application examples

Special training on laying a solid foundation - analysis of error-prone concepts

Decide whether the following statements are correct or incorrect, and analyze and correct the incorrect statements.

()1. An electric energy meter is an instrument that measures the electrical power consumed by electrical appliances.

Analysis and correction: ______________________________________________________________________.

()2. The more turns the turntable on the electric energy meter rotates, the greater the total power of the electrical appliances connected to the circuit where the electric energy meter is located.

Analysis and correction: ______________________________________________________________________.

()3. Large electrical power means that the current does work quickly.

Analysis and correction: ______________________________________________________________________.

()4. The more work done by the current passing through the electrical appliance, the greater the electrical power of the electrical appliance.

Analysis and correction: ______________________________________________________________________.

()5. Both kilowatts and kilowatt hours are units of electrical power.

Analysis and correction: ______________________________________________________________________.

Specialized training for energy improvement—analysis of key test points

Test point 1 Electric energy, electric energy meter

The understanding of electric energy and the use of electric energy meters are closely related to daily electricity consumption. There is a tendency to increase the intensity of examinations in the propositions of each province. However, because the knowledge is relatively simple, the test mainly consists of fill-in-the-blank questions and multiple-choice questions.

Example 1 Figure 18-T-2 shows the dials of Xiao Ming’s electric energy meter at the beginning and end of last month respectively. “1600 imp/(kW·h)” on the dial indicates that every 1 kW·h of electricity consumed, the indicator light flashes. 1600 times, the correct one among the following options is ()

A． The faster the indicator light flashes, the more energy is consumed by the circuit where the energy meter is located.

B． The electricity consumed by Xiao Ming’s home last month was 911 kW·h

C. The current in Xiaoming's main circuit must not exceed 10 A

D. Disconnect other electrical appliances and only let the rice cooker work alone

2 minutes, the indicator light flashes 32 times, the power of this rice cooker is 600 W

Test point 2 Electric power

The knowledge point of electrical power is a key and difficult point in electricity. The test content mainly includes the understanding of electrical power and simple calculation of electrical power; in the high school entrance examination, it is often tested in the form of fill-in-the-blank questions, multiple-choice questions, and calculation questions.

Example 2 Connect lamp L1 to a circuit with a voltage of 6 V, and its electric power is 6 W. If the power supply voltage remains unchanged, then connect lamp L2 to the circuit, as shown in Figure 18-T-3. The following statement The correct answer is (regardless of the effect of temperature on the filament resistance) ()

A． The total resistance of the circuit is 18 Ω

B． The actual current through lamp L1 is 0.5 A

C. Lamp L2 emits dimmer light than lamp L1

D. The total power of the circuit is 4.5 W

Test Point 3 Joule’s Law

Joule's law is an extension of electrical energy knowledge and a focus of electricity. The examination content mainly includes the application of electric heat, the harm of electric heat, and the calculation of electric heat. In the high school entrance examination, it is mainly presented in the form of fill-in-the-blank questions and multiple-choice questions.

Specialized Experimental Training—Key Experimental Breakthroughs

Experiment 1: Measuring the electrical power of a small light bulb

Example 5 In the experiment of "Measuring the electrical power of a small light bulb", the experimental equipment includes: battery pack (voltage is constant at 3 V), ammeter, voltmeter, small light bulb (rated voltage is 2.5 V), sliding rheostat, switch, and several wires , the physical circuit is shown in Figure 18-T-6A.

(1) Please use pen lines instead of wires to completely connect the physical circuit in Figure A.

(2) Connect the circuit, close the switch, and adjust the sliding rheostat. It is found that the small bulb does not light up, the voltage indication is always zero, and the current indication changes significantly. The circuit fault may be ____________________.

(3) Conduct experiments after troubleshooting. Figure B shows the I-U image of the small light bulb drawn from the experimental data. The rated power of the small light bulb is ________W. When the small light bulb emits light normally, the resistance of the sliding rheostat connected to the circuit is ________Ω.

(4) Analyzing the I-U image of the small light bulb, it is found that the resistance of the filament of the small light bulb changes with the change of voltage. Essentially, the factor that causes the change of the resistance of the filament of the small light bulb is ____________.

[Variation extension] Explore the following questions based on the above example:

(1) When Xiao Ming adjusted the sliding rheostat for measurement in the experiment, he burned out the filament (the remaining components were intact), so the voltage indicated at this time was approximately ________V.

(2) When Xiaohua was processing the experimental data, he calculated the average power of the small light bulbs (as shown in the table below). Do you think it is ______ (choose "reasonable" or "unreasonable") to process the data in this way. Reason: _______________________________________________________________________________________________.

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For more information about the PPT courseware "Improvement of Core Competencies in this Chapter of Electric Power", please click on the ppt tag of "Improvement of Core Competencies in this Chapter of Electric Power ppt".

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