2. Magnets: Objects with magnetism are called magnets. It is directional: it refers to the north and south.
3. Magnetic pole: The part with the strongest magnetism on the magnet is called the magnetic pole.
(1) Any magnet has two magnetic poles, one is the north pole (N pole); The other is the South Pole.
② Interaction between magnetic poles: the same name magnetic poles repel each other, and the different name magnetic poles repel each other.
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Attract each other.
4. Magnetization: The process of magnetizing an object without magnetism.
5. There is a magnetic field around the magnet, and the interaction between magnetic poles occurs through the magnetic field.
6. Basic properties of magnetic field: apply magnetic force to the magnet inserted into it.
7. Magnetic field direction: At a certain point in the magnetic field, the direction in which the north pole points when the small magnetic needle is stationary is the direction of the magnetic field at that point.
8. Magnetic induction line: an imaginary curve describing the strength and direction of the magnetic field. The magnetic induction line around the magnet comes from its north pole and returns to the south pole. (The magnetic induction line does not exist, and it is indicated by a dotted line and does not intersect. )
9. The direction of the magnetic field and the direction of the magnetic induction line are the same as the direction of the north pole when the small magnetic needle is at rest.
10. The geomagnetic north pole is near the geographical south pole; The geomagnetic south pole is near the geographical north pole. (The north and south poles of geomagnetism do not coincide with the north and south poles of geography, and their intersection angle is called magnetic declination, which was first described by China scholar Shen Kuo. )
1 1. Oster experiment proves that there is a magnetic field around the electrified wire.
12. Ampere's Law: Hold the solenoid with the right hand and bend it in the direction of the current in the solenoid with four points, then the end pointed by the thumb is the north pole (N pole) of the solenoid.
13. Ampere rule is easy to remember and use: I will see you when I enter the wire, holding it in my hand; If the thread is missing, hold it back. One end of the thumb is the North Pole (N Pole).
14. Characteristics of energized solenoid: ① The greater the current, the stronger the magnetism; ② The more turns of the coil, the stronger the magnetism; ③ Inserting a soft iron core greatly enhances the magnetism; ④ The polarity of the energized solenoid can be changed by the current direction.
15. electromagnet: a solenoid with an iron core inside constitutes an electromagnet.
16. characteristics of electromagnet: ① magnetism is controlled by the on-off of current; ② The magnetic force can be adjusted by changing the current and the number of turns of the coil; ③ The current direction can change the magnetic pole.
17. electromagnetic relay: it is essentially a switch controlled by an electromagnet. Its function can realize remote operation and control high voltage and strong current with low voltage and weak current. But also can realize automatic control.
The answer to the optimization design of Zhihong in the second volume of the eighth grade
Such a question feels meaningless.