"Magnetic Phenomena: Magnetic Field" Electricity and Magnetism PPT (Lesson 1 Magnetic Phenomena)

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"Magnetic Phenomena: Magnetic Field" Electricity and Magnetism PPT (Lesson 1 Magnetic Phenomena)

Part One: Knowledge Management

1. Two properties of magnets

Iron attraction: the property of attracting iron, cobalt, nickel and other substances.

Directivity: Hang a permanent magnet so that it can rotate freely. When it comes to rest, one end always points to the south (S) pole, and the other end points to the north. The end pointing to the north is called the north (N) pole. ) extremely.

2. The law of interaction between magnetic poles

Rule: Magnetic poles with the same name repel each other, and magnetic poles with different names attract each other.

3. magnetization

Concept: Some objects acquire magnetism under the action of magnets or electric current. This phenomenon is called magnetization.

Magnetic Phenomenon and Magnetic Field PPT, Part 2 Content: Classification and Exploration

Type one: interaction between magnetic poles

[2017•Tianjin Nankai District]When Xiaohong was studying magnetic phenomena, she brought two steel rods A and B with the same shape in the laboratory. In order to judge the magnetic properties of the steel rods, Xiaohong did She did a small experiment and found that when one end of A is close to one end of B, and B rotates as shown in the picture, then Xiaohong can judge (C)

A. It must be that rod A is magnetic and rod B is non-magnetic.

B． It must be that rod B is magnetic and rod A is non-magnetic.

C. Both A and B may be magnetic

D. Both A and B must be magnetic

Type 2: Magnetization

[2018•Jiaxing, Zhejiang]Use the N pole of a bar magnet to rub a thick sewing needle in the same direction several times to magnetize the sewing needle, as shown in Figure A. Then hang the sewing needle with a thin thread, as shown in Figure B. Which of the following statements is correct (C)

A. After the sewing needle is magnetized, the needle tip is the S pole.

B． When a sewing needle stops moving, its tip points south

C. When a sewing needle stops moving, its tip points north

D. After the sewing needle stops moving, the needle tip points uncertainly.

[Analysis] After repeatedly rubbing one pole of the magnet on the sewing needle from the tip to the tail of the needle several times, the sewing needle is magnetized; at the last contact position between the magnet and the sewing needle, that is, the N pole of the magnet is in contact with the sewing needle. When the needle tails of the needle are in contact with each other, the needle tail of the sewing needle and the N pole of the magnet attract each other. According to the interaction between the magnetic poles: magnetic poles with the same name repel each other, and magnetic poles with different names attract each other. The needle tail is the S pole, then The needle tip is the N pole. Hang the sewing needle with a thin thread. After the sewing needle stops moving, the needle tip (N pole) points to the north, so C is correct. So choose C.

Magnetic Phenomenon and Magnetic Field PPT, Part 3: In-person Evaluation

1. [2018•Hunan Xiangxi Prefecture] Which of the following objects can be attracted by magnets (　D　)

A. Eraser b. plastic triangular plate

C. Charcoal d. nails

2. [2017•Hubei Wuhan]As shown in the figure, two steel rods A and B with the same appearance attract each other, then (　D　)

A. Rod A must be magnetic

B． Rod A must not be magnetic

C. Rod B is not necessarily magnetic

D. Rod B must be magnetic

3. As shown in the figure, A is an iron rod and B is a small magnetic needle. Put the N pole of the magnet close to the iron rod. It is found that one pole of the small magnetic needle near the lower end of the iron rod is repelled, while the other pole is attracted. From the analysis of this phenomenon, it can be seen that the following is consistent with the experimental facts: (D)

A. When the iron rod A is magnetized, the upper end is the N pole, and the pole to which the small magnetic needle is attracted is the N pole.

B． When the iron rod A is magnetized, the upper end is the N pole, and the pole to which the small magnetic needle is attracted is the S pole.

C. When the iron rod A is magnetized, the upper end is the S pole, and the pole to which the small magnetic needle is attracted is the N pole.

D. When the iron rod A is magnetized, the upper end is the S pole, and the pole to which the small magnetic needle is attracted is the S pole.

[Analysis] It can be seen from the figure that the lower end of the magnet is the N pole. After the iron rod A is magnetized, the upper end is the S pole and the lower end is the N pole. The magnetic poles with different names attract each other, so the pole that the small magnetic needle is attracted to is the S pole, so D correct.

Magnetic Phenomenon and Magnetic Field PPT, Part 4: Layered Operations

1. [2018•Gansu Tianshui]A magnet is embedded in the coffee cup so that the cup, saucer and spoon can adhere to each other and will not fall even if it is turned upside down. An ingenious design must capture the curiosity of every new user. The magnet coffee cup can make people mistakenly think it is a fake one-piece piece. If the spoon can be absorbed by the magnet coffee cup, the material for making the spoon may be (B)

A. silver b. Stainless steel

C. Aluminum D. copper

2. [2018•Zigong, Sichuan]A student from Zigong used the bar magnet in his hand to conduct the following experiment. The correct conclusion is (B)

A. Magnetic poles with the same name attract each other

B． Bar magnet attracts small nails

C. A bar magnet is suspended from a thin wire so that when it is at rest in a horizontal plane, the north pole points to the geographical south.

D. After a thin layer of glass is separated between the bar magnet and the small magnetic needle, there is no interaction.

3. [2018•Zhejiang Quzhou]During class, the teacher touches two pins to one end of the magnet, and the pins are attracted to hang under the magnet. As shown in the picture, the needle caps of the two pins will be (B )

A. Attract each other b. Mutually exclusive

C. Neither attracting nor repelling D. unconfirmed

[Analysis] The two pins have been magnetized when they are attracted by the magnet. The end close to the magnet is magnetized into a magnetic pole with a different name, and the end far away from the magnetic pole is magnetized into a magnetic pole with the same name as the magnetic pole. The needle caps of the pins in this question are all magnetized into The S pole, the magnetic poles with the same name repel each other.

4. [2018•Guangdong Shantou]As shown in Figure A, a bar magnet is broken into two sections. Take the right section close to the small magnetic needle. When the small magnetic needle is at rest, the direction is as shown in Figure B, then the right section The magnetic pole of the crack is the N pole; if this piece of magnet is placed together along the crack (as shown in Figure A), the two pieces will attract each other (optional "attraction" or "repulsion"); this illustrates the interaction between the magnetic poles Magnetic poles with the same name repel each other and magnetic poles with different names attract each other.

5. [2018•Zhejiang Taizhou]As shown in the figure, a small iron block weighing G slides from the N pole to the S pole along the surface of the bar magnet under the action of the horizontal force F. The following statement The correct one is (B)

A. The friction force on the small iron block keeps getting smaller and smaller

B． The gravitational force exerted on the small piece of iron remains the same.

C. The pressure of the small iron block on the magnet remains unchanged

D. The pressure of the small iron block on the magnet first increases and then decreases

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Update Time: 2024-11-04

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