Monday, January 3, 2011

【 Weak current College 】 e-mail production started with 100 questions (2) 】

2. knowledge of electronic components
51, resistors in circuits basic do?
Resistor in a circuit called resistance, to limit the size of the current, allocate the required voltage. Hereinafter referred to as "limited that partial pressure effect".
52, how to represent in general circuit resistance of resistance?
General circuit resistance unit is omitted from the direct use of numeric representation. Greater than 1000 Ohm resistance number use the "K". Greater than 1000K using the "M" rate.
53, opposite points of resistance is expressed resistance? for example four color ring resistance.
Use color rings represent the numeric value, the former second ring represents a valid number, and the third ring represents the rate, or the number of zero. The fourth indicates that error.
54, opposite points of resistance and the corresponding color is how?
Brown Red 1, 2, 3, Orange, green, yellow 5, 4, 6, 7, 8, purple, white ash, black 0 9; gold 0.1, silver 0.01
55, select what you want to pay attention to resistors with two parameters?
Resistance nominal value and the nominal power.
56, capacitors have?
The capacitor capacitance for short, has a storage capacity of the electric charge, starting from the circuit, the "communication" and that "impacted DC-resistance of high frequency, low frequency", etc.
57, why can store charge capacitor?
Capacitor consists of two pieces are very close and mutually insulated metal conductors, connect and then disconnect the power, because "opposite attracts the principle of" positive and negative charges will remain on the plate, stored charge, the greater the distance between the plates area, closer and more storage charge.
58, capacitor charging and discharging is all about?
Both ends of the capacitor connected to power, the plates will be stored on a certain amount of the charge, the procedure call charging. Disconnect the power supply, connect the load has a charge of the capacitor at bothends, because there the difference of both ends, the capacitor will produce a current until the capacitor storage in charge all release, a process called discharge.
59, how to represent the capacitance of the capacitor?
The basic unit of electrical capacity is "Farra" symbol "F"-practical in smaller units, such as micro-Farah (μ F) and Farah (pF).
1 Farah = 1000000 micro-method 1 micro-method = 1000000 skin method
60, capacitor type is divided?
Capacitor can be divided into fixed and variable capacitor capacitance. Middle insulation distinguish most direct extraction of capacitor insulation materials to name. When there is a selection of capacitors for high frequency circuit, a capacitor is polarity, pay attention to when the access circuit connection.
61, capacitor value is common representation? examples.
The smaller of the capacitor common digital representations, that is, with three digits indicate the capacitance, the first two digits are the digits, the first three digits mean effective digital back to increase the number of zero, the basic unit is a skin method. If 471 is 4700pF. 10000pF 103 is equivalent to 0.01 μ F.
62, is the same as the value of the two capacitance of the capacitor series and parallel with the tolerance value?
The same as the value of the two capacitance of the capacitor capacity of the small series, parallel capacity.
63, selection of capacitors should pay attention to?
Selection of capacitors should be aware of the capacitor capacitance nominal value and pressure values.
64, capacitor why to "communication"?
AC electrical signal corresponds to an AC power supply, its polarity and size over time changing, capacitor connected to AC circuits, AC signals at both ends of the polar changes in capacitance, equivalent to a capacitor ongoing new round of charging and discharging process is just as capable of conducting.
65, inductors are based on what principle work? what role?
Inductors are based onthe work of electromagnetic induction principle, have the will power and energy conversion of the role played in the circuit of the "save energy" and "resistance" AC, DC.
66, commonly used inductors types?
Including the radio-frequency transformers, magnetic coils, ordinary power transformers, inductors color-coded, and so on.
67, color code inductance is all about, the basic unit of inductance?
Some small fixed inductors, use color-coding indicates inductance inductance, known as the color code. Inductor of energy storage special performance measured with inductance, whose basic unit is Henry, expressed by the symbol H, smaller units-enjoy (mH) and enjoy (μ H).
68, brief inductors composition?
Inductors are generally around with enameled wire coil skeleton completed intermediate often equipped with magnetic core materials, inductor with shielded enclosures.
69, transformer works?
Two parallel abutting coils, due to electromagnetic induction principle, a coil current change will cause another add-in into a Loop Electrosurgical produce changes in the current and two coil voltage ratio equal to the number of turns of the coil.
70. What is electro-acoustic devices? examples.
The electrical signal into sounds of devices such as: speakers, headphones and sound into an electrical signal from devices such as microphones, collectively known as electro-acoustic original. Piezoelectric ceramic plate is also an audio converter.
71. What is RC circuit? what role?
The resistance and capacitance circuit that combines RC circuit resistance, resistance to control the size of the current charging and discharging control capacitance voltage change at both ends or slow speed, RC circuit also called time circuit, may constitute a timer, etc.
72. What is LC circuit, what role?
The inductor and capacitor connected to circuit, called LC circuit. LC circuit with select signal frequency.
73, semiconductor have any characteristic of the most important characteristics of??
Semiconductor conductivity varies with temperature, light intensity and doping impurities. The most important characteristic of semiconductors is doped different impurities, its conductive "free of charge" polarity can change.
74, semiconductor devicesCore?
75, brief pn junction diode characteristics? main features?
P-type semiconductor rely on "free positive charge" conductive, N-type semiconductor rely on "freedom of negative charge" the formation of conductive, combination with unidirectional pn junction, conductive, semiconductor diode is a PN structure.
76, which mainly using diode to? examples.
Semiconductor diodes are used to operating current, a reverse voltage does not exceed the corresponding technical parameters. If the led current limiting resistor, with its current may exceed and burned. It must not be led directly to the power supply circuit formation.
77, please give examples of three or more common diode?
There is a light-emitting diodes, Zener diodes, rectifier diode detector tubes, etc.
78, transistor's main structure and main types?
Semiconductor transistor triode also known, consists of two PN structure. According to two different PN combination, can be divided into PNP and NPN-type.
79, general purpose transistor has three electrodes pin, say its name and written symbols?
Transistor's three electrodes are launching set e, the base c b, collector.
80, transistor circuit can work in which three States? what application?
Globe, zoom, on-. Closing and on-State commonly used to switch circuit. Zoom status is radio technology in the most extensive triode applied.
81, transistor DC amplification is how to work out?
Collecting electrode electric current changes in the volume and the base current changes in the ratio of the amount that is DC amplification.
82, what transistor DC biasing circuit?
Let the transistor work in the State, require prior use resistors assignedthe extremely good transistor DC voltage, the circuit is called the bias circuit.
83, transistor or low according to the operating frequency is divided into two major categories which? mutually substitution?
Can be divided into low-frequency and high frequency tubes and pipes, General low frequency and high frequency tubes not substitution and high frequency tubes can be substitution corresponding working conditions of low frequency.
84, transistor's main parameters?
DC amplification coefficient β value; penetrate current Iceo.; collector maximum allowable current Icm collector a launch Breakdown voltage Vceo; collector maximum dissipation power Pcm. Low-voltage low-power conditions most critical parameters DC amplification coefficient β value.
85, how to use multimeter judged commonly used silicon transistor's three electrodes and type?
Use the internal power supply is greater than the 9V R×1K multimeter find fixed a table pen press a electrodes, another table amount respectively to touch the remaining two pins are on-State, if red table amount fixed by the electrode is PNP-transistor and the electrode to b, in the case of a black table amount fixed by the electrode is a NPN-type and the electrode for b; and then use the red and black table pens respectively two electrodes, if the pointer is greater apparent swing instruction, PNP type red table amount of $ c is very, very for NPN-type e; the black table amount received as PNP-NPN-type e very, very c. The above test, the attention to exclude human resistance on the impact of ohmic stall b must be vacated and the rest of the electrode is not exposed. You can also use the finger contact b, estimating the size of DC amplification ability to judge the e, c.
86, what is the short circuit??
The diode, triode parts RC components and circuit wiring all centralized production in a semiconductor substrate, constitute a unit short circuit, called IC IC.
87, integrated circuits, and there is no exploitation.
Reduce electronic circuits of solder joints, increase reliability, reduce circuit circuit size and weight, to electronic devices in miniature of the creation of favorable conditions.
88, application of the IC should pay attention to what matters?
Identify the circuit diagrams in the PIN and the correspondence between physical, master common IC packaging of PIN number rule, lap peripheral component that provides the correct power supply voltage, prevent damage to the IC.
89, how to tell if a diode pin polarity?
Some diodes have one end of the loop flag is negative, the light-emitting diode's long foot as positive. You can also use multimeter test, Omron stalls breakover, black table pen to cathode and anode red table for the pen. Light-emitting diode with power greater than 3V measurement of ohm stalls.
90, in General, what are the characteristics of photosensitive?
Ray ensues, the smaller the resistance; light weaker, the greater the resistance.
91, introduction to integrated circuits Repeater-radio works?
Magnetic coils and resonant capacitor LC circuit consisting of antenna selection space radio signals into electrical signals, input to the Repeater type radio LC zoom, demodulation broadcasting audio signal output after the audio amplifier enlarged advance electro-acoustic devices emit radio sound.
92, low Assembly experimental Board completed the experimental circuit should pay attention to what matters?
Identification experiments on electrical conduction between Jack and insulation. For integrated circuit, transistor and light emitting diode, pin easily broken components, try not to pin piece too large, and in the Assembly order, first arrange these components positioning, spelled plug other long foot components. Spell plug, note that homeopathy firmly to avoid bending pin, make sure that Jack Reed and PIN contact good.
93, small Assembly experiment kit 9012, 9013, D7642 are three electrodes components, please indicate what devices?
9012-PNP-transistor NPN, 9013-type transistor, D7642 as Repeater-radio IC.
94, what does the LM386?
LM386 is a commonly used audio power amplifier IC.
95, correct circuit diagram is like?
Circuit diagram is a diagram that clearly mark the graphic symbols representative of electronic components, circuits and wires connected location. In accordance with the electricityRoad map marked content, select the appropriate electronic components, the correct connection is completed, will achieve the intended function.
96, what words commonly used in the circuit diagram symbol represents resistors, capacitors, transistors, diodes, inductance coil number prefix?
R = resistance, capacitance, VT C indicates that transistor, diode, VD said L represents the inductor.
97, how to distinguish polarity capacitor pin polarity?
Long foot is positive, negative short legs. Most of the negative polarity capacitor will be in package on the skin, the corresponding PIN is the anode.
98, the former three rings for Brown Brown, Brown, red, Brown, yellow, brown orange ring resistance, corresponding to the nominal value of specific?
100 ohms, 1K ohm, 100K ohm, 10K ohm.
99, the former fourth ring of rings black and red to Brown resistance standard values?
100, ceramic capacitor 471, 103, 104, please indicate the maximum and minimum capacitance of the capacitor?
471 minimum, 104 maximum.

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