"Starting from Permanent Magnets" Electromagnets and Automatic Control PPT Courseware

Description

"Starting from Permanent Magnets" Electromagnets and Automatic Control PPT Courseware

1. Magnet: A magnetic object is called a magnet.

(1) Magnetism: The property of an object to attract iron, cobalt, nickel and other substances is called magnetism.

(2) Magnet classification: temporary magnets and permanent magnets

Artificial magnets and natural magnets

The difference in shape can be divided into:

(bar magnet) (hoof magnet) (small magnetic needle)

experiment

Spread the iron filings evenly on the white paper, place the magnets flat on the iron filings, then lift the magnets and observe the phenomenon.

The magnet is strongest at both ends of the magnet

The middle has the weakest magnetism

Magnetic pole: The strongest magnetic part of a magnet.

2. Magnetic pole

The end of the magnet pointing north is called the North Pole, represented by N.

The south pole on the magnet is called the south pole, represented by S.

The magnetic poles are the strongest magnetic parts of the magnet.

Any magnet has two magnetic poles and they exist inseparably at the same time.

3. The law of interaction between magnetic poles

Magnetic poles with the same name repel each other,

Magnetic poles with different names attract each other.

4. Experimental study of magnetization and demagnetization

Magnetization: The process of making a non-magnetic object acquire magnetism is called magnetization

Magnetization method:

(1) Place one pole of the magnet close to or in contact with steel, iron and other substances

(2) Rub one pole of the magnet on the steel needle several times in the same direction.

Demagnetization: making the originally magnetic steel needle lose its magnetism

Demagnetization method:

(1) Keep tapping

(2) Place it on the flame to heat

A magnetic field is a substance that exists around a magnet.

1. Basic properties of magnetic field:

It exerts a magnetic force on the magnet placed inside it. The interaction between magnets occurs through magnetic fields.

2. Direction of magnetic field:

It is stipulated that at a certain point in the magnetic field, the direction pointed by the north pole when the small magnetic needle is stationary is the direction of the magnetic field at that point.

How to visually represent the direction and strength of the magnetic field at each point in the space around the magnet?

Remove some iron filings evenly on a glass plate, then place the glass plate on the bar magnet and observe any changes in the distribution of the iron filings. Tap the glass plate lightly and observe any changes in the distribution of iron filings.

Activity:

Use iron filings to show the magnetic field distribution of a permanent magnet

the way is:

1. Place the bar magnet on the white paper, and then place the glass plate flat on the magnet.

2. Sprinkle a small amount of iron filings evenly on the glass plate

3. Tap the glass plate lightly.

4. Draw the distribution of the magnetic field you see

Characteristics of magnetic field lines:

1) Outside the magnet, the magnetic field lines run from the north pole (N pole) of the magnet to the south pole (S pole) of the magnet.

2) The direction of the magnetic field lines is the direction of the force exerted on the north pole of the small magnetic needle at that point. That is the direction the north pole points when the small magnetic needle comes to rest.

3) The place where the magnetic field lines are dense indicates the strength of the magnetic field at that point, that is, the density of the magnetic field lines indicates the strength of the magnetic field.

4) There is only one magnetic field direction at each point in space, so the magnetic field lines do not intersect.

practise

1. The property of an object that can attract iron-containing objects is called __ __Objects with this property are called ______

2. The strongest magnetic part of a magnet is _______. This part is called _________, which are called ____ pole and ____ pole respectively.

3. Tie a thin wire to the middle of a bar magnet and hang it in still air. You can find that the bar magnet always points in the _______ direction. The N pole of the bar magnet refers to ______ ______ and the S pole refers to _ _____

4. Use the N pole of the bar magnet to get close to the A end of an object. If you find that it can attract the A end, then the A end of the object ( )

A is a certain S pole, B may be an N pole

C may be the S pole. D must be the N pole.

5. One end of an object is close to a stationary small magnetic needle. When it is close to the N pole and S pole of the small magnetic needle, it is attracted. Then this end of the object ( )

A may be non-magnetic B may be N pole

C may be the S pole. D must be magnetic.

Tips for using magnets

1. Magnets are brittle, so be careful when using them. They can easily break if dropped.

2. After the magnet is used, if it is a bar magnet, it must be placed in pairs, and the N pole of magnet A and the S pole of magnet B must be close to each other. If it is a hoof magnet, an armature must be added to the opening to prevent loss of magnetism. .

3. Do not store magnets near fire; minimize collisions when using them to prevent premature weakening of magnetism.

4. If the magnetism of the needle magnet is found to be too weak, you can use the N pole (or S pole) of a stronger magnetic bar magnet and gently rub it twice from the N pole (or S pole) of the magnetic needle toward the S pole (or N pole). , which can greatly increase the magnetism of the small magnetic needle.

Do it: Sense the presence of magnetic fields

1. Place the small magnetic needle at a certain point around the bar magnet and observe the direction of the small magnetic needle when it is stationary; gently move the small magnetic needle with your hand. How does the direction of the small magnetic needle change?

2. When a position is changed, does the direction of the small magnetic needle change?

3. Let the small magnetic needle slowly rotate around the magnet. What do you find?

What do the above experimental phenomena indicate?

1. Magnet

1. Magnet: able to attract steel, iron, nickel and other substances

2. Magnetic poles: The magnetism is strongest at both ends of the magnet. The magnetism in other parts is relatively weak, and the magnetism in the middle is the weakest.

Each magnet has two magnetic poles, one is called the south pole, also called the S pole, and the other is called the north pole, also called the N pole.

3. The rules of interaction between magnetic poles:

Magnetic poles with the same name repel each other, while magnetic poles with different names attract each other.

4. Properties of magnets: magnetism and directivity

2. Experimental study of magnetization and demagnetization

1. Magnetization: The process of making a non-magnetic object acquire magnetism is called magnetization.

2. Magnetization method:

(1) Place one pole of the magnet close to or in contact with steel, iron and other substances

(2) Rub one pole of the magnet on the steel needle several times in the same direction.

3. Demagnetization: Make the original magnetic steel needle lose its magnetism

4. Demagnetization method:

(1) Keep tapping

(2) Place it on the flame to heat

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"Starting from Permanent Magnets" Electromagnets and Automatic Control PPT Courseware 2:

"Starting from Permanent Magnets" Electromagnets and Automatic Control PPT Courseware 2 1. Magnets 1. The properties that can attract iron, cobalt, nickel and other substances are called: magnetism. 2. Magnetic objects are called magnets. 3. Classification of magnets: artificial magnets and natural magnets..

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Update Time: 2024-08-30

This template belongs to Physics courseware Guangdong and Shanghai Edition Ninth Grade Physics Volume 2 industry PPT template

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