Top 100 basic knowledge of electronic manufacturin

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Introduction to electronic production 100 questions

1. What is electricity? How many kinds of electricity? What are the important characteristics of electricity

electricity is an attribute of the real object first shown in the phenomenon of friction electrification. There are two kinds of electricity: positive and negative. The same sex repels each other and the opposite sex attracts each other is an important characteristic of electricity

2. How to understand that electricity is an attribute of physical objects

electricity comes from the real object itself. Generally, the real object itself has an equal amount of positive and negative charges, so it does not show the characteristics of electricity; For some reason, when the physical object loses or obtains a certain charge, it will show the electrical characteristics externally

3. Friction electrification is the only way for an object to become charged. Please explain

No. In addition to friction, heating, chemical changes and other reasons may make objects become charged

4. What are conductors and insulators? Examples

objects that are easy to conduct electricity are called conductors; Objects that are extremely difficult to conduct electricity are called insulators. Metals and aqueous solutions with impurities are conductors; Plastic, air and dry wood are insulators

5. The plastic rod can absorb the small paper gauze after rubbing with wool, but the metal object can't, so the metal object can't rub and electrify, right? Why

no, metal objects can also be electrified by friction, just because the metal is a good conductor, and the charge will soon be neutralized by the human body's discharge to the ground, so it does not show a charged state

6. Are all conductors of the same conductivity

different. For example, copper has better conductivity than aluminum, and aluminum has better conductivity than iron. The conductivity of aqueous solution with impurities is poor, but it is still a conductor

7. Why is it easy for conductors to conduct electricity? And insulators are not easy to conduct electricity

there are movable charges in the conductor, and there are very few movable charges in the insulator, so the conductor is easy to conduct electricity, while the insulator is not easy to conduct electricity

8. Is the insulator not conductive under any circumstances? Examples

No. If air reaches a certain strength under voltage, it will be ionized and become a conductor. Lightning is a natural phenomenon that air suddenly becomes a conductor under high-voltage static electricity

4. Adopt two colors of double window lipstick and green

9. What is the breakdown phenomenon

the substance that used to be an insulator turns into a conductor under a high-voltage electric field. This phenomenon is called breakdown phenomenon. Lightning is a phenomenon in which air is broken down by high-voltage static electricity

10. Why does the human body conduct electricity

human body contains a large amount of aqueous solution with other substances dissolved, so it will also conduct electricity

11. How is the current formed

the charge that can move freely in the conductor moves regularly under the action of external power, and then forms current

12. Which scientist is the name of the unit indicating the magnitude of current? What is his main contribution

the unit of current is named after the French scientist ampere. The main contribution of ampere is to study and determine the force relationship between current and magnetic field

13. How is the direction of current in the conductor specified

the direction of current is customarily positive in the direction of positive charge movement

14. What does a metal conductor rely on to conduct electricity and what is its moving direction

metal conductors rely on free electrons that can move freely to conduct electricity. Free electrons are negatively charged, and their moving direction is opposite to that of positive charges

15. I often hear about AC and DC. What's the matter? Examples

the direction of the working current does not change with time is called DC. The magnitude and direction of the working current change with time is called alternating current. The flashlight is a direct current working mode, and the household incandescent lamp lighting is an alternating current working mode

16. What about voltage

just as the water level difference will maintain the water pressure, the potential difference will also produce an electric force on the charge, which is also called voltage

17. Which scientist is the unit of voltage taken from? What is his main contribution

the unit of voltage is taken from the name of volt, the abbreviation of volt, the symbol V, of the scientist who invented the volt battery. His main contribution was the invention of volt battery, which created extremely important conditions for the utilization and research of electricity

18. What is safe voltage

for human body, voltage greater than 36V will be life-threatening. Therefore, the voltage less than 36V is called safety voltage

19. Give examples of voltage values often encountered in daily life

the voltage of civil AC is 220V; The nominal value of a dry cell is 1.5V; The nominal voltage of a nickel cadmium rechargeable battery is generally about 1.2V; The voltage of each group of lead-acid battery is about 2V. Wait

20. How to use dry batteries to get higher voltage

a voltage of 1.5V times can be obtained by connecting dry cells in series. For example, 3V can be obtained by connecting two batteries in series and 4.5V can be obtained by connecting three batteries in series

21. What is power supply? Examples

devices that convert other forms of energy into electrical energy are called power supplies, such as dry batteries that convert chemical energy into electrical energy: generators that convert mechanical energy into electrical energy; Solar cells convert solar energy into electricity and so on

22. What is the difference between DC power supply and AC power supply? Please explain

the power supply that provides DC form is called DC power supply, the power supply that provides AC form is called AC power supply, civil AC is AC power supply, and dry battery is DC power supply

23. What is load? Examples

in contrast to the power supply, a device that converts electrical energy into other forms of energy is called a load. For example, electric lamps convert electric energy into light energy, and electric motors convert electric energy into mechanical energy

24. Who invented the commonly used electric lamp, that is, the incandescent lamp

Edison, American inventor

25. What are the characteristics of magnetic field

there are always two regions with opposite polarity and the strongest magnetic force, which are called magnetic poles. Magnetic poles are divided into North Pole (n) and south pole (s), and their characteristics are: the same polarity repels each other, and the different polarity attracts each other

26. How does the magnetic field come into being

the moving charge generates a magnetic field, and the magnetic phenomenon comes from the movement of the charge

27. Who was the first scientist to reveal that electricity can produce a magnetic field

in the 1920s, the Danish physicist Auster first demonstrated to the public the experiment that the electrified conductor made the magnetic needle rotate, thus revealing the close relationship between electricity and magnetism

28. What does the compass phenomenon mean

the compass, first invented by the Chinese, shows that there is a large magnetic field on the earth

29. Who was the first scientist to realize magnetoelectricity

in 1831, Faraday, a British scientist, realized the scientific experiment of magnetoelectricity and discovered the phenomenon of electromagnetic induction

30. Who discovered electromagnetic waves

when Maxwell, a British scientist, summed up the previous research results on electricity and magnetism with mathematical methods, he calculated that the changing electromagnetic field would propagate in its surrounding space and form electromagnetic waves

3 in food packaging. 1. Who is the first scientist to confirm the existence of electromagnetic waves? What physical unit does his name denote

15 years after Maxwell put forward the electromagnetic wave theory, the German youth Hertz developed a clever device, which confirmed the electromagnetic wave theory for the first time. His name refers to the unit of frequency

32. What is electromagnetic wave frequency

the number of electromagnetic periodic changes completed in unit time is called electromagnetic wave frequency, and its unit is Hertz, which is abbreviated as Hertz, and the symbol is Hz. Commonly used units include kHz (kilohertz) and MHz (megahertz)

33. Are radio waves and visible light the same in nature

yes, both radio waves and visible light are electromagnetic waves, but the frequency is different, and the radio wave frequency is low. Radio waves travel at the same speed as visible light

34. What is the relationship between wavelength and frequency

the electromagnetic wave completes an electromagnetic periodic conversion, and its propagation distance is called the wavelength. Wavelength is the speed of light divided by frequency. The higher the frequency, the shorter the wavelength

35. What is the difference between medium wave and short wave radios

according to the corresponding relationship between frequency and wavelength, the receiving frequency between 500KHz and 1600khz is a medium wave radio, and the receiving frequency between 3MHz and 30MHz is a short wave radio

36. Which two scientists were the first to realize the radio communication experiment

Italian Marconi and Russian Popov. Marconi also won the Nobel Prize

37. What is amateur radio communication activity

amateur radio communication activities, as an amateur business, are included in the international telecommunication treaty, which refers to the business that is not for financial interests, but for individuals who are interested in radio technology and engage in self-training, communication and technical research with proper permission. Enjoy the radio frequency resources allocated by the International Telecommunication Union to amateur radio enthusiasts for free, study, research and practice electronic technology, communication technology and information processing technology, and significantly enhance the knowledge and ability of participants in technology, language, humanities and geography

38. What is a circuit? What are the three elements of circuit

The path of current is called a circuit. The circuit must be closed, that is, the charge flows out of the positive pole of the power supply and must return to the negative pole of the power supply to form a current. Therefore, the circuit is also called an electrical circuit. Power supply, load and wires connecting them to form a loop are essential elements of any circuit

39. How many states does the circuit have? What is the most dangerous state

the circuit has three states: first, the circuit is connected everywhere to form a loop. 2、 A circuit that breaks somewhere cannot form a loop, which is called an open circuit or an open circuit. 3、 The accidental conduction of the two ends of the original voltage in a part of the circuit is called short circuit. Among them, short circuit may damage the power supply device and components, which is in a dangerous state and must be avoided

40. What is resistance? Which scientist named the unit of resistance? His main contribution

the part of the circuit that hinders the passage of current and causes energy loss is called resistance. The unit of resistance is named after the German physicist ohm. His main contribution is to study the relationship between voltage, current and resistance through a large number of experiments, and summarize the most basic circuit law Ohm's law

41. What is Ohm's law

The current in the conductor is directly proportional to the voltage at both ends of the conductor and inversely proportional to the resistance of the conductor. Or when the resistance is constant, the current increases with the increase of voltage, and when the voltage is constant, the current decreases with the increase of resistance

42. What is series connection and parallel connection? Assume that the load is two bulbs

there are two possible connections of two bulbs in the circuit. If two bulbs are connected one by one in sequence, it is called series connection. Connecting the two ends of two bulbs side by side is called parallel connection

43. Are the two resistors in series, the greater or the minimum resistance? Parallel connection

series connection is larger, and parallel connection is smaller

44. How to understand electric power? How to express its size

in the process of different forms of energy conversion, work can be used to express their quantitative relationship. The energy of current is transferred to the load and converted into other quantities, which can be expressed by electric work. Electric work is equal to the product of electricity and voltage, and its unit is usually kilowatt hour. KWh

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