"Charge Triboelectricity" Current and Circuit PPT Courseware 2

"Charge Triboelectricity" Current and Circuit PPT Courseware 2

Have you ever seen this phenomenon?

When the air is dry and the hair is combed with a plastic comb, the hair will "float" with the comb;

Why do you think this happens? Have you seen similar cases in your life?

Do it

Using friction to charge an object is called triboelectricity.

1. Frictional electrification

If a rubbed object can attract light and small objects, it means that the object is charged, that is, the object has an electric charge. This phenomenon is called frictional electrification.

(Electric objects are also called "charged objects")

Charging an object by friction is called triboelectricity

1. Two kinds of charges

interaction between charges

Any charged object that repels a glass rod rubbed with silk must be attracted to a rubber rod rubbed with fur.

Like charges repel each other,

Different charges attract each other.

1. There are only two types of charges in nature

Regulation:

The charge on a glass rod rubbed with silk is called a positive charge;

The charge on a rubber rod rubbed with fur is called a negative charge.

2. Like charges repel each other, and dissimilar charges attract each other.

3. The amount of charge is called charge.

Unit: Coulomb, abbreviation: Coulomb, symbol: C

Two charged bodies with charges of 1 coulomb each are 1 km apart, and the interaction force is about 9 000 N. It can be seen that the Coulomb is a very large unit.

4. Use a glass rod rubbed with silk to get close to the light ball. If the ball is repelled, the ball is ( )

A. Positively charged B. Negatively charged

C. Uncharged D. May be negatively charged or uncharged

2. Atoms and their structures

1. Common substances are composed of molecules and atoms.

2. Atomic structure

3. Causes of frictional electrification

The atomic nuclei of different substances have different abilities to bind electrons.

An object that has lost electrons becomes positively charged because of the lack of electrons;

The object that received the electrons has the same amount of negative charge because of the excess electrons.

Triboelectricity does not create electric charges, but simply transfers electric charges from one object to another, separating positive and negative charges.

3. Conductors and insulators

1. Experimental Study

Experiment 1: Connect the electroscope with a rubber rod

Experimental phenomena

The opening angles of the metal foils of electroscopes A and B do not change.

experiment analysis

The charge of electroscope A has not changed, and electroscope B is still uncharged.

Experiment 2: Use a metal rod to connect two electroscopes

Experimental phenomena

The opening angle of the metal foil of electroscope A decreases, and the metal foil of electroscope B changes from closed to open.

experiment analysis

Electroscope B is also charged. Some of the charge moves from A to B through the metal rod, and the charge moves in a directional manner.

Experimental results

Charges can move directionally in metals, indicating that metals can conduct electricity.

2. conductor

(1) Objects that easily conduct electricity are called conductors.

(2) Common conductors: metal, human body, earth, graphite, salt water solution, etc.

(3) Reasons why conductors conduct electricity:

There are free charges in a conductor

Metals: free electrons

Salt solution: anion cation

3. insulator

(1) Objects that do not conduct electricity easily are called insulators.

(2) Common insulators:

Rubber, glass, plastic, air, oil, etc.

(3) Reasons why insulators are not easy to conduct electricity:

Electric charges are bound to atoms and molecules and cannot move freely.

practice

1. Regarding insulators, which of the following statements is correct ( )

A. Insulators cannot conduct electricity under any circumstances

B． Insulators do not conduct electricity easily and cannot be charged

C. Insulators do not conduct electricity easily, but they can carry electricity

D． There are no electrons in an insulator, so it does not conduct electricity easily

2. Normally, the group of the following objects that are insulators is ( )

A. Human body, earth, copper key

B． Rubber, kerosene, plastic bags

C. Pencil lead, salt water, glass

D． Porcelain bottle, air, steel ruler

Classroom targeted exercises

1. Use your hands to rub the loose plastic packaging rope. The more times you rub it, the phenomenon you will see is: _______. Can you analyze the reason?

2. When a positively charged object comes into contact with the metal ball of the electroscope, the metal foil opens because of _________

Use your hands and brain

As shown in the picture, use a piece of thin wire to make a bracket and a rotating shaft. Place a beverage straw with a hole poked in the middle (not pierced) on the rotating shaft. The straw can rotate freely on the horizontal plane. Rub the straw with a napkin to make it electrified.

(1) Put an object near one end of a charged straw and find that the straw is approaching the object. Can you judge that the object is charged?

(2) Place the silk-rubbed glass rod near one end of the charged straw, observe the direction of movement of the straw, and answer: What kind of electricity does the straw carry? What kind of electricity do napkins carry? Why?

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