"Starting from Lightning" explores simple circuit PPT courseware

Description

"Starting from Lightning" explores simple circuit PPT courseware

learning target

1. Understand the phenomenon of frictional electrification.

2. Know the rules of two kinds of charges and their interaction.

3. Know that lightning is an instantaneous large-scale discharge phenomenon.

Core test points: Frictional electrification, interaction between charges

Preview before class

1. (2015·Zhengzhou Yimou) When the plastic comb used to comb dry hair is close to the thin water flow, the phenomenon as shown in the picture will be observed. This is because the comb will attract the thin water flow after _____ after friction. ． When the comb came close to the glass rod rubbed by the silk, it was found that the glass rod was repelled, indicating that the comb was _____ charged.

2. If two charged rods A and B repel each other, then ( )

A. The two rods have the same charge B. Two rods with different charges

C. Both rods must be positively charged D. Both rods must be negatively charged

Lectures in class

Knowledge point 1. Frictional electrification

(1) The object is charged: The friction of an object can attract other light and small objects. We say that this object is charged, or charged for short.

(2) Triboelectricity: Using friction to electrify objects is called triboelectricity. The phenomenon of triboelectricity is very common in life. There is lightning on clothes at night, and dust is easy to stain on clothes. When you comb your hair with a comb, the hair floats with the comb. wait.

(3) Two kinds of charges: There are only two kinds of charges in nature. In 1747, American scientist Franklin stipulated that the charge of a glass rod rubbed with silk is called positive charge; the charge of a rubber rod rubbed with fur is called negative charge.

[Typical Example 1] (2014·Rizhao) Among the following phenomena, what is caused by frictional electrification ( )

A． If you take off your sweater in dry weather, you will hear a slight crackling sound B. When playing the erhu, the friction between the bow hair and the strings will produce sound C. When your hands feel cold in winter, rubbing your hands together will warm them up

D. Rub the steel needle along the magnet a few times, and the steel needle will attract iron filings

[Exercise 1] (2014·Changzhou) After the rubber rod rubs against the fur, the rubber rod becomes negatively charged. This is because the friction makes the rubber rod ( )

A． Lose some electrons B. get some electrons

C. Lose some protons D. get some protons

Knowledge point 2. Interaction between charges

The law of interaction between charges: like charges repel each other, and dissimilar charges attract each other.

Note: The law of interaction between charges is the basis for distinguishing positive and negative charges, and is also the basic principle of the electroscope.

[Typical Example 2] (2014·Jiangxi) As shown in the figure, grass balls A and B repel each other, and A and C attract each other. If A is known to be positively charged, then the charging conditions of B and C are ( )

A． B is negatively charged, C is positively charged

B． B is positively charged, C is positively charged

C. B is negatively charged, C is negatively charged or uncharged

D. B is positively charged, C is negatively charged or uncharged

[Exercise 2] (2015•Wuhan Simulation) There are three light and small objects A, B, and C. Object A repels object B, and object B attracts object C. Which of the following statements is correct ( )

A． If object A is positively charged, then object C must be positively charged

B． If object A is positively charged, then object C must be negatively charged.

C. If object A is negatively charged, then object C must be positively charged.

D. If object A is negatively charged, object C may not be charged

Knowledge point 3. Discharge phenomenon

(1) Discharge phenomenon: When the heterogeneous charges between two objects accumulate to a certain extent, spark discharge will occur. For example, lightning is an instantaneous large-scale discharge phenomenon between clouds with different charges, or between charged clouds and the earth.

【Example 3】Thunder and lightning often occur when dark clouds roll in the rainy season. This is because ( )

A． Dark clouds roll and friction generates heat

B． Dark clouds release stored solar energy

C. Discharge occurs in clouds with different charges

D. Discharge occurs in clouds with the same charge

[Exercise 3] Xiao Ming saw an eye-catching slogan at the gas station: "Plastic barrels are strictly prohibited to transport gasoline." Xiao Ming has the following understanding of this. Do you think the correct one is ()

A. The gaps between the molecules that make up plastic are very small, so gasoline will seep out of the plastic barrel continuously.

B. The chemical reaction between gasoline and plastic barrels will cause the plastic barrels to melt.

C. When the car is running, there is constant friction between gasoline and plastic, and too much accumulated charge can easily cause discharge and cause a fire.

D. Plastic is a good conductor of heat. Cars generate heat when running. The heat is transferred to the gasoline through the plastic barrel and reaches the ignition point, which will cause a fire.

In-class testing

1. Use a plastic comb to comb dry hair a few times. The comb will be charged. After testing, the comb is negatively charged. Which of the following statements is correct ( )

A． Friction creates electric charge

B． The comb got some electrons

C. The comb lost some electrons

D. The comb lost some of its nuclei

2. (2014•Hulunbuir) There are three light balls A, B, and C. It is known that A is negatively charged, A and B attract each other, and C and A repel each other, then ( )

A． B must be uncharged, C must be positively charged

B． B may be positively charged, and C may be positively charged.

C. B must be positively charged and C must be negatively charged

D. B may be uncharged and C may be negatively charged

3. (2014•Yiyang) Take two identical electroscopes A and B, make A charged and B uncharged. You can see that the metal foil of A is open and the metal foil of B is closed (as shown in the picture). Use a metal rod with an insulated handle to connect the metal balls on A and B. Then the changes in the opening angles of the metal foils of A and B ( )

A． A and B remain unchanged

B． A becomes smaller, B expands

C. A becomes larger and B remains unchanged.

D. A is closed, B is open

4. Which of the following are phenomena to prevent static electricity ( )

A.Electrostatic dust removal B.Electrostatic copying

C. Oil tanker truck mopping the floor with chains D. Electrostatic spraying

5. (2014 Henan) The rubber rod rubs against the fur. The rubber rod becomes negatively charged due to _____ electrons. Put the negatively charged rubber rod close to the plastic straw that has been rubbed against the work paper. It is found that the straw is pushed away, indicating that the straw is ____ _electricity.

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Update Time: 2024-09-06

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

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