"What is Electricity" Understanding Circuits PPT Courseware 3

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"What is Electricity" Understanding Circuits PPT Courseware 3

1. Frictional electrification phenomenon

See the image below of this girl's hair after coming into contact with a charged metal ball

Why does her hair stand up?

Using friction to charge an object is called triboelectricity.

in conclusion:

Some objects can attract light and small objects after being rubbed. This phenomenon is called the object being charged, or "charged".

Frictional electrification: Using friction to charge objects is called triboelectricity.

Properties of charged bodies: Charged bodies can attract light and small objects.

2. Two kinds of charges

Experiments and Observations

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

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.

3. Electroscope

structure:

Metal balls, metal rods, metal foil

working principle:

Like charges repel each other

Function: Check whether the object is charged

The larger the opening angle of the electroscope, the more charge it carries.

4. Atoms and their structures

1. Common substances are composed of molecules and atoms.

2. Atomic structure

3. Element charge (e): The smallest amount of charge is called element charge

e＝1.6×10-19C

4. Under normal circumstances, the number of positive charges carried by the nucleus is equal to the total number of negative charges carried by all electrons outside the nucleus. The entire atom is neutral, which means that the atom does not appear to be charged to the outside.

Think about it: Is this oxygen atom charged?

Think about it: Is this oxygen ion charged?

5. The essence of frictional electrification:

When two objects rub against each other, the object with a strong ability to bind electrons loses electrons and becomes negatively charged, while the object with a weak ability to bind electrons loses electrons and becomes positively charged.

Strong gains negative, weak loses positive.

When silk is rubbed against a glass rod, the silk's ability to bind electrons is strong, and the resulting electrons are negatively charged; the glass rod's ability to bind electrons is weak, and the lost electrons are positively charged.

The essence of triboelectricity: the gain and loss of electrons

Class summary

1. Two kinds of charges

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

1. There are only two kinds of charges in nature: positive charge and negative charge.

2. Interaction between charges

Like charges repel each other and dissimilar charges attract each other

3. Charge amount

The amount of charge is called charge. Unit: Coulomb (C)

4. Electroscope

Function: Check whether the object is charged

Principle: Like charges repel each other

2. Atoms and their structures

1. Common substances are composed of molecules and atoms.

2. People call the smallest charge an element charge, which is often represented by the symbol e. e=1.6×10-19C

practice

1. The charge generated by triboelectricity has brought a lot of trouble to people in production and life. Among the following phenomena, the ones that are not caused by triboelectricity are ( )

A. In the dry autumn and winter seasons, when you take off your sweater at night, you will find some small sparks, which will cause pain to your skin.

B． Clothes made of chemical fiber fabrics tend to absorb dust

C. When you touch an outdoor iron rod with wet hands in winter, your hand will get stuck to the iron rod.

D． In dry weather, when you comb your hair with a plastic comb, your hair will fly with the comb.

[Analysis] Choose C. When you touch an iron rod outdoors with wet hands in winter, the water freezes when it becomes cold, causing your hand to stick to the iron rod. This is a solidification phenomenon; while the other three phenomena are due to frictional electrification. caused, so choose C.

2. When weaving a certain kind of carpet, some stainless steel wires are mixed in during the weaving process. This is because ()

A. Make the carpet look better

B.Make the carpet more durable

C. Make carpets better at conducting heat

D. Release static electricity to make the carpet less likely to be stained with dust.

[Analysis] Choose D. When people walk and rub against the carpet, it will become charged and attract dust in the air. When weaving the carpet, some stainless steel wires are mixed in. Since the stainless steel wire is a conductor, it can release static electricity, making the carpet less likely to be stained with dust.

3. CCTV’s “Samsung Intelligence Express” program introduced that bees fly and friction with the air generates static electricity, so bees can attract positively charged pollen during flight. The following statement is correct ( )

A. Bees are negatively charged B. Bees are positively charged

C. Air is uncharged D. Air is negatively charged

[Analysis] Choose A. Static electricity is generated by bees and air friction. Then the bees and the air are both charged bodies and have different charges. Bees and positively charged pollen attract each other and attract each other based on different charges. Therefore, the bees are negatively charged and the air is. It is positively charged, so choose A.

4. (2010·Chongqing High School Entrance Examination) In preparation for the high school entrance examination, Nan Nan prepared: ① transparent plastic pencil case ② metal blade ③ plastic triangular plate ④ pencil lead ⑤ eraser and other items. Among the above five items, some of them are insulators. ( )

A.①③⑤ B.②④⑤

C.③④⑤ D.①②④

[Analysis] Choose A. Objects made of plastic and rubber are all insulators. A is correct; blades and pencil leads made of metal and graphite are all conductors. B, C, and D are wrong.

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For more information about the PPT courseware "Understanding What Electricity Is a Circuit", please click the "Understanding What Electricity Is a Circuit ppt" ppt tag.

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Update Time: 2024-10-03

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