"Understanding Electric Power" Electric Energy and Electric Power PPT Courseware

Description

"Understanding Electric Power" Electric Energy and Electric Power PPT Courseware

【learning target】

1. Understand electrical power with examples and know the units of electrical power.

2. Know the relationship between electric power, current and voltage, and be able to use the formula of electric power to perform simple calculations.

3. Experience the experimental exploration process of "exploring what factors are related to the electric power of the light bulb", learn to apply the knowledge of series and parallel circuits to design circuits, and experience how to use control variables in experiments.

Core test points: Calculation of electrical power, general examination comprehensive questions.

【Preview before class】

1. The electrical power of an electrical appliance is equal to the ______ it consumes in _____, so "100W" means that the electrical energy consumed by this electrical appliance in _____ is _____.

2. There are two lights in Xiaoli's room, one is a lighting lamp marked with "PZ220�40", and the other is a nighttime emergency backup light marked with "36V�40W". When the two lights are working normally, _____ lights up.

[Intensive lectures in class]

Knowledge point 1. Electric power

In physics, the ratio of the electrical work done by a current in a certain period of time to this period of time is called electrical power, and electrical power is represented by P. The size of the electrical power reflects the size of the effect produced by the electrical appliance through the consumption of electrical energy. If the electrical appliance is used The greater the electrical power, the more electrical energy is consumed per unit time, expressed by the formula: P=W/t.

P——Electrical power——Watt (W)

W——The work done by the current——Joule (J)

t - time taken - seconds (s)

The international unit of electrical power is watt (W), referred to as watt, and the commonly used unit of electrical power is kilowatt (kW).

Notice:

①The function of electric power is to describe how quickly the current does work. Electrical appliances with high electric power can only mean that the electrical appliance consumes electric energy quickly or the current does work quickly, but it does not mean that the current does more work.

② Electric power can reflect the effect produced by electrical appliances when they pass through current. For example, if the electric power of the light bulb is large, it means that the current does more work through the light bulb per unit time, which means that the light bulb consumes more electrical energy per unit time, so the brightness of the light bulb is greater.

Knowledge point 2. Explore what factors are related to the electric power of the light bulb

1. Conjecture and hypothesis:

The electrical power of a light bulb may be related to voltage, current, or both.

2. Experimental equipment:

Power supply, two voltmeters, two ammeters, two light bulbs of different specifications, switches, and some wires.

3. Design experiments:

Experimental research should be carried out through the control variable method. When studying the relationship between electric power and current, the voltage should be controlled constant; when studying the relationship between electric power and voltage, the current should be controlled constant.

a. When exploring the relationship between electric power and voltage, the current should be kept the same and the electrical appliances should be connected in series. During the experiment, two light bulbs with different specifications are connected in series in the circuit (as shown in Figure A), and the voltage at both ends of the light bulb is observed and compared. and the brightness of the light bulb.

b. When exploring the relationship between electric power and current, the voltage should be kept the same and electrical appliances should be connected in parallel. During the experiment, two light bulbs with different specifications are connected in parallel in the circuit (as shown in Figure B), and the current flowing through the light bulbs is observed and compared. and the brightness of the light bulb.

[In-class testing]

1. The rated electrical power of household air conditioners is approximately ()

A． 1 500 watts B. 150 watts c． 15 watts D． 1.5 watts

2. (2014·Guangyuan) As shown in the figure, when the switch is closed and the sliding plate of the sliding rheostat is slid upward, the observed phenomenon is (　)

A． The bulb dims and the voltage indication increases.

B． The light bulb becomes brighter, but the voltage indicated remains unchanged.

C． The total power consumed by the circuit becomes smaller, and the voltage representation remains unchanged.

D. The total power consumed by the circuit becomes larger, and the voltage representation number becomes larger.

3. (2014•Yunnan) When winter comes, Xiao Wang bought a "hand warmer" for his grandma. The relationship between the electric heat generated during the heating process of the "hand warmer" and time is shown in the figure. From this, it can be seen that the power of the "hand warmer" during heating is approximately ( )

A． 2400W b． 400W c. 40W D. 24W

4. (2014·Guang'an) As shown in the figure, the power supply voltage remains unchanged, the small bulb L is marked with "6V 0.6W", R is a fixed value resistor, close S1, open S2, the small bulb emits light normally; If S2 is closed again, it is found that the current indication has changed by 0.3A, then the resistance value of R is _____Ω. At this time, the ratio of the power consumed by the bulb L and the resistor R is _____.

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For more information about the "Electric Energy and Electric Power Understanding Electric Power" PPT courseware, please click the Electric Energy and Electric Power PPT Understanding Electric Power PPT tab.

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Update Time: 2024-06-29

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

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