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.

18. electromagnetic induction: when a part of the conductor of a closed circuit cuts a magnetic induction line in a magnetic field, a current is generated in the conductor. This phenomenon is called electromagnetic induction, and the generated current is called induced current.

19. Conditions for generating induced current: ① The circuit must be closed; (2) Only a part of the conductor of the circuit is in the magnetic field; (3) This part of the conductor cuts the magnetic induction line.

20. Direction of induced current: It is related to the direction of conductor movement and the direction of magnetic induction line.

2 1. In electromagnetic induction, mechanical energy is converted into electrical energy.

22. The principle of generator is based on electromagnetic induction. Alternator is mainly composed of stator and rotor.

23. High-voltage transmission principle: keep the output power unchanged, increase the transmission voltage and reduce the current at the same time, thus reducing the loss of electric energy.

24. Influence of magnetic field on current: The electrified wire will be affected by magnetic force in the magnetic field. Convert from electrical energy to mechanical energy. The application is to manufacture motors.

25. Force direction of charged conductor in magnetic field: It is related to the direction of current and the direction of magnetic induction line.

26.DC motor principle: it is made by using the principle that the electrified coil is forced to rotate in the magnetic field.

27. alternating current: current that periodically changes the direction of current.

28. Direct current: current with constant direction.

Chapter 17 Electromagnetic Wave and Modern Communication Knowledge Induction

1. information: meaningful information sent by various things.

In human history, information and information dissemination activities have undergone five major changes: ① the birth of language; (2) the birth of characters; (3) the birth of printing; ④ Application of electromagnetic wave; ⑤ Application of computer technology. (Requirements will be sorted correctly)

2. Early information dissemination tools: beacon towers, post horses, telegrams, telephones, etc.

3. Tools for storing information are: ① ox bones, bamboo slips, wooden slips, ② books, ③ disks and CDs.

4. All waves are propagating periodic motion patterns. For example, water and rubber rope spread in the form of alternating concave and convex, while spring and sound wave spread in the form of alternating density.

5. Mechanical wave is the propagation of vibration form in medium, which not only propagates the form of vibration, but also mainly propagates the energy of vibration. When information is loaded on a wave, it can be spread out.

6. Physical quantities describing the nature of waves: ① Amplitude A: the distance from the equilibrium position of the wave source, in M2Period T: the time required for the wave source to vibrate once, in S3Frequency F: the number of times the wave source vibrates per second, in Hz. ④ wavelength λ: the distance that the wave travels in the periodic category, in m. 2009 Shanghai Yangpu Senior High School Entrance Examination English Zhenti and Answers 2009 Shanghai Zhabei Senior High School Entrance Examination English Zhenti and Answers 2009 Shanghai Xuhui Senior High School Entrance Examination Math Zhenti and Answers 2009 Shanghai Baoshan Senior High School Entrance Examination Math Zhenti and Answers 2009 Shanghai Chongming Senior High School Entrance Examination Math Zhenti and Answers View all senior high school entrance examination literature resources >>