"Electric Power" Electric Power PPT Teaching Courseware (Lesson 1)

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"Electric Power" Electric Power PPT Teaching Courseware (Lesson 1)

Part One: Knowledge Management

1. Electric power

Physical meaning: Electric power is a physical quantity that expresses how quickly a current does work, that is, a physical quantity that expresses how quickly an electrical appliance consumes electrical energy.

Definition: The work done by electric current per unit time.

Unit: The basic unit is watt (W), the commonly used unit is kilowatt (kW), 1 kW = 1 000 W.

2. Calculation of electrical power

Definition formula: P=Wt (universally applicable).

Calculation formula: P = UI (universally applicable).

Derivation formula: P = I2R = U2R (only applicable to pure resistive circuits).

Explanation: (1) Transform the formula P=Wt to ​​W=Pt. Use this formula to find the electrical work done by the current.

(2) Transform the formula P=UI to I=PU or U=PI. Using these two formulas, the current and voltage can be obtained.

(3) Combining the formula W=Pt and the formula P=UI, we can get: W=UIt. Using this formula, we can find the work done by the current.

Note: (1) Electrical appliances that convert all electrical energy into internal energy are called pure resistance appliances, such as resistance wires, etc.;

(2) When the current is constant (such as a series circuit), it is known from P=I2R that the electric power is proportional to the resistance;

(3) When the voltage is constant (such as a parallel circuit), it is known from P=U2/R that the electric power is inversely proportional to the resistance.

Electric power PPT, part 2: classification and exploration

One type: understanding of electrical power

[2018•Hunan Zhuzhou]When the power consumption of a smartphone reaches a certain amount, the user will automatically be prompted to adopt the "power saving mode". In this mode, the battery power supply time can be extended because (B)

A． Reduced battery output voltage

B． Reduces battery output current

C. Reduces the resistance of electronic circuits

D. Increased battery output power

[Analysis] The working voltage of the mobile phone is certain. If the output voltage of the battery is reduced, the mobile phone will not work properly, so A is wrong. The power stored in the mobile phone battery is certain. According to the formula W = Pt, we need to extend the working time of the mobile phone. The output power needs to be reduced, but the operating voltage of the mobile phone is unchanged. From P = UI, in the power saving mode, the output current of the battery should be reduced, so B is correct; the structure of the internal electronic circuit of the mobile phone is unchanged, Therefore, the resistance is also constant, so C is wrong; from the formula W=Pt, we know that increasing the output power of the battery will shorten the working time of the mobile phone, so D is wrong. So choose B.

[Summary] According to the formula W = Pt, the "power saving mode" of a mobile phone is to extend the use time by reducing the output power under the premise that the mobile phone battery stores a certain amount of energy.

Type 2: Electric power rules of series and parallel circuits

[2017•Guangxi Hechi]As shown in the figure, the power supply voltage is 12 V and remains unchanged, R1 is a fixed-value resistor, and R2 is a sliding rheostat (a and b are its two end points). Close the switch S. When the slide P is at the end point a, the current is 0.1 A, and the electric power consumed by R2 is 1 W. When the slide P moves to a certain position c, the voltage is 4 V, and the power consumed by R1 is 4 V. The electrical power is 3.2 W. Which of the following statements is correct (C)

A． When the slide P is at point a, the electrical power consumed by R1 is 2 W.

B． When the slider P is at point b, the electrical power consumed by R1 is 0.6 W.

C. When the slide P is at point c, the electrical power consumed by R2 is 1.6 W

D. When the slider P is at point c, the total power consumed by the circuit is 4 W

[Method Summary] Pay attention to the fact that the current in the series circuit is equal everywhere. Understanding the current under different voltages can solve the problem of electric power consumed by electrical appliances.

Electric power PPT, the third part: in-person evaluation

1. The physical quantity that expresses the speed of work done by electric current is (　D　)

A． Electric current B. Voltage

C. Electric power D． Electric power

2. [2019•Putian, Fujian]The resistance of the two resistance wires R1>R2, the relationship between the electrical power after they are energized is (　C　)

A． From P=I2R, it can be seen that P1>P2

B． It can be seen from P=U2R that P1

C. When the currents through R1 and R2 are equal, P1>P2

D. When the voltages at both ends of R1 and R2 are equal, P1>P2

3. [2019•Zhangjiakou, Hebei]The voltage across a conductor increases from 3 V to 6 V, and the current in the conductor increases by 0.6 A. Then the changes in the resistance of the conductor and its electric power are respectively ( B)

A． 5 Ω, 1.8 W B. 5Ω, 5.4W

C. 10 Ω, 16.2 W D. 10Ω, 1.8W

4. [2018•Zigong, Sichuan]There is an electric soldering iron. If it is in the same lighting circuit and its electric power needs to be smaller, the following modification methods are feasible (　C　)

A． Cut off a small section of the resistance wire

B． Replace with a thicker resistance wire

C. Connect a resistor in series with the resistor wire

D. Connect a resistor in parallel with the resistor wire

Electric power PPT, part 4: layered operations

1. [2019•Jiangsu Yancheng]Which of the following statements about electric power and electric power is correct (B)

A． Electric power is a physical quantity that represents how much electrical energy is consumed

B． Electrical power represents the physical quantity of how quickly electric current does work.

C. The greater the power of an electrical appliance, the more work it does

D. Appliances that are powered on for a long time consume a lot of electricity.

2. [2019•Shanxi Yuncheng]Xu Yang used an electric energy meter to measure the electrical power of a household appliance. When only this electrical appliance is working in the circuit, it is measured that the power consumed is 0.2 kW·h within 10 minutes, then this electrical appliance may be (　A　)

A． Air conditioning b. refrigerator

C. TV D. radio

3. [2018•Shenyang, Liaoning]As shown in the figure, the power supply voltage remains unchanged, R1=15 Ω, switch S1 is closed, switch S2 is opened, the current value is 0.2 A; switches S1 and S2 are closed at the same time , the current expressed number is 0.5 A. At this time, the electric powers of R1 and R2 are P1 and P2 respectively. Which of the following is correct (B)

A． P1∶P2＝2∶3　R1∶R2＝2∶5

B． P1∶P2＝2∶3　R1∶R2＝3∶2

C. P1∶P2＝3∶2　R1∶R2＝2∶5

D. P1∶P2＝3∶2　R1∶R2＝3∶2

4. [2018•Tianjin]In the circuit shown in the figure, the power supply voltage remains unchanged, and the ratio of the resistance values ​​of resistors R1 and R2 is 2:1. When switch S is open, the ratio of the electric power of R1 and R2 is 2:1; before and after switch S is closed, the ratio of the two readings of the voltmeter is 2:3.

5. [2019•Nanjing, Jiangsu]A small light bulb is marked with the words "6 V3.6 W". The curve of the relationship between the current I and the voltage U at both ends is as shown in the figure. When the voltage across the small bulb is 3 V, the resistance of the small bulb is 6 Ω and the electric power is 1.5W.

Keywords: Free download of PPT courseware for ninth-grade physics from the People's Education Press, download of electrical power PPT, download of two sets of unit problems in the simple application of formulas, .PPT format;

For more information about the PPT courseware "A simple application of the electric power formula using two sets of unit problems", please click the "A simple application of the electric power ppt formula using two sets of unit problems ppt" tag.

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Update Time: 2024-07-06

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