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46483 2008 年 01 月 13 日 01:20 Reading (loading. ..) Comments (0) Category: Original Literature
current
directional movement is called the charge circuit, current common I said. Both DC and AC Current. The size and direction of the current does not change over time is called the DC. Current size and direction of change over time is called the exchange. Current unit is safe (A),
mulberry bags, also commonly milliamps (mA) or microamps (uA) to do unit. 1A = 1000mA, 1mA = 1000uA. Current can be measured with the ammeter. When measured, the ammeter in series in the circuit, to select the pointer close to the full deflection of the ammeter scale. This prevents excessive current damage meter.
voltage
the river was able to flow because the water level is poor; charge was able to flow because there is potential difference. Is the voltage potential difference. Voltage causes the formation of current. In the circuit, the voltage used U said. Voltage is volt (V), also commonly used in millivolts (mV) or microvolts (uV) make units. 1V = 1000mV, 1mV = 1000uV. Voltage can be measured with a voltmeter. Measurement time, the voltmeter in parallel in the circuit, the table pointer to select the voltage close to full scale deflection. If the voltage on the circuit size estimates do not come out first with a large range, a rough measurement and then with the appropriate range. This prevents excessive damage due to voltage voltmeter.
circuit resistance on the current role and through obstacles caused by the energy consumption of the part is called resistance. Resistance of common R said. Unit of resistance is the European (Ω), also commonly used kilohms (kΩ) or megohms (MΩ) made units. 1kΩ = 1000Ω,
burberry bags, 1MΩ = 1000000Ω. Resistance of the conductor from the conductor material, cross-sectional area and length of the decision. Resistance can be measured with a multimeter ohm file. Measuring time, deflected to choose nearly half of the meter pointer Ohm file. If the resistance in the circuit, make a hot open after resistance measurement.
Ohm's law conductor current I and the conductor is proportional to the voltage U, and the conductor resistance R is inversely proportional, that is, I = U / R. This rule is called Ohm's law. If you know the voltage, current, resistance, volume two of the three, according to Ohm's law to find the third volume, that is, I = U / R, R = U / I, U = I × R
in AC circuit, Ohm's law also set up, but the impedance of resistor R should be changed to Z, that is I = U / Z
power
to other forms of energy into electrical energy device called a power supply. Generator can convert mechanical energy to electrical energy, batteries can convert chemical energy into electrical energy. Generators, batteries and so called power. Through the transformer and rectifier, the alternating current into a device called a rectifier DC power supply. To provide an electronic device called a signal source. Transistor can be amplified before the signal sent, again amplified the signal sent to the back of the circuit to go. Transistor on the back of the circuit, can also be seen as the source. Rectifier power supply, sometimes called the power source.
load
to other forms of energy can be converted into a device called a load. Motor can convert electrical energy into mechanical energy, electrical energy can converted into heat resistance, light bulbs can heat and light energy into electrical energy, the speaker can sound energy into electrical energy. Motors, resistors, light bulbs, speakers, and so is called the load. Transistor source for the front, it can also be seen as a load.
circuit current flows through the road called the circuit. The simplest circuit consists of power supply, load and wires, switches and other components. Circuit is called the channel connected everywhere. Only path, the circuit current to flow in. Disconnect the circuit is called a circuit or open circuit. Circuit is directly connected to both ends of a part, so that this part of the voltage to zero, called the short circuit.
EMF EMF to reflect the power to other forms of energy into electric energy of the ability of physical quantities. Electromotive force generated across the power supply voltage. In the circuit, the EMF used δ said. Force units and units of the same voltage is volts.
force power can voltmeter. When measured, the power receiving circuit to do with the voltmeter across the power supply voltage, the voltage value obtained can be seen as equal to the power of the force. If the power supply connected to the circuit, with a voltage meter measured the voltage across the power supply will be less than the power of the force. This is because the power supply has internal resistance. In the closed circuit, current through the resistor r are within the voltage drop through the external resistor R with foreign pressure drop. Δ is equal to the power of the EMF voltage and external voltage UR of Ur, ie, δ = Ur + UR. Strictly speaking, even if the power does not access circuit, a voltmeter measuring the voltage across the power supply, voltage meter into the external circuit, the voltage is less than the measured force. However, due to a large internal resistance of voltage meter, power supply internal resistance is small, the voltage can be ignored. Therefore, the power supply voltage meter measured the voltage across the power supply can be regarded as equal to the EMF.
batteries worn, with the voltage by measuring the voltage across the battery, and sometimes still relatively high, but can not access the circuit after the load (radios, tape recorders, etc.) normal work. This is because the larger internal resistance of the battery, even bigger than the load resistance,
designer handbags, but still better than the small internal resistance of voltage meter. With a voltmeter across the battery voltage when the battery voltage within the share of internal resistance is not large, so the voltage meter measured the voltage is still relatively high. However, access to the circuit the battery, the battery voltage within the share of internal resistance increases, the voltage on the share of the load resistance decreases, the load can not work properly. In order to determine the old battery can not be used, when the load should be measured in a voltage across the battery. Some poor performance of the power supply, a load and no load in both cases measured the voltage difference between the larger power supply, but also because the larger the power supply caused by internal resistance.
AC cycle to complete a full change is called the cycle time required, usually T said. Period is in seconds (s), also commonly milliseconds (ms) or microseconds (us) to do unit. 1s = 1000ms, 1s = 1000000us.
AC frequency
cyclical changes in the 1s to complete the number of known frequency, commonly used f said. The unit is Hz frequency (Hz), also commonly kilohertz (kHz) or megahertz (MHz) to do unit. 1kHz = 1000Hz, 1MHz = 1000000Hz. AC frequency f is the reciprocal of period T, that is
f ; = 1 / T
capacitor conductor capacitance is a measure of physical ability to store charge. In the two mutually insulated conductors, coupled with a certain voltage, they will save some power. Save one of the conductors with a positive charge, and the other conductor save the negative charge of equal size. Coupled with the greater the voltage, the more storage capacity. Storage capacity and coupled with the voltage is directly proportional to their ratio is called the capacitance. If the voltage is expressed by U, Q, said electricity use, said capacitor with C, then
C = Q / U
capacitor unit is France (F), also commonly used in microfarads (uF) or slightly Act (pF) to do unit. 1F = 106uF, 1F = 1012pF.
capacitor capacitor tester can measure, you can also file with the multimeter ohms rough estimation. Ohmmeter red, black pen were two tables of the feet touch the capacitors, Ohm table will charge the capacitor battery, the pointer deflection, charge finished, the pointer back to zero. Exchange of red and black two tables T, and then will reverse charging capacitor discharge. Capacitance greater the greater the deflection of the pointer. Compare the measured capacitance and the capacitance of the deflection of known cases, a rough estimate can be measured capacitance value. Electronic circuits in general, in addition to other needs tuning circuit capacitor capacity of more than accurate, the most used blocking, bypass capacitors, filter capacitors, capacitors do not need the capacity and accurate. Thus, a rough estimate capacitance values Ohm file is meaningful. But ordinary multimeter ohms file can only estimate the value larger capacitance value of capacitance necessary to use smaller value resistors in the transistor large files multimeter ohms to estimate, slightly less than the dozens of law The capacitance tester had measured using a capacitance.
anti
content is through ac capacitor, but the capacitance of the AC still have them back. Impediment to the AC capacitor is called capacitance. Large capacity, easy to pass the AC capacitor,
alexa mulberry, indicating large capacity capacitor hinder small; high frequency alternating current, AC is also easy to pass capacitor, indicating that high frequency capacitance impediment is also small. Experimental results show that capacitance and the capacitance is inversely proportional, and the frequency is inversely proportional. If the capacitance with XC, said capacitor with a C, said the frequency indicated by f, then
; XC = 1 / (2πfC)
capacitance of the unit is the Euro. Know the frequency f and the capacitance of the AC C, can be used for type to calculate the capacitance.
inductance inductance electromagnetic induction coil is a measure of physical ability. Pass into the current to a coil, the magnetic field is generated around the coil, the magnetic flux through the coil there. Coil power leads to greater, the stronger the magnetic field, the greater the magnetic flux through the coil. Experiments show that the magnetic flux through the coil and access to the current is directly proportional to the ratio of their inductance is called, also known as inductance. If the magnetic flux through the coil indicated by φ, the current use of I said that the inductor with L, then
; L = φ / I
unit of inductance is Henry (H), also commonly used millihenry (mH) or micro-Henry (uH) to do unit. 1H = 1000mH, 1H = 1000000uH.
anti
sense can also ac coil, the coil inductance on the AC but hinder the role of the obstacles is called reactance. Inductor volume, difficult to pass the AC coil, indicating that large inductors, inductance major impediment; high frequency alternating current, alternating current through the coil is difficult to illustrate high frequency inductor impediment is also large. Experiments show that the inductance and inductance is proportional, and proportional to frequency. If the inductive reactance XL with said inductor with L said that the frequency with f, then
; XL = 2πfL
inductance of the unit is in Europe. Know the frequency f and the AC coil inductance L, can be used for type to calculate the inductance.
Resistance
with resistance, inductance and capacitance circuit, the obstacles on the role played by alternating current is called impedance. Common impedance Z said. Resistance and the resistance, inductance and capacitance composed of three, but not a simple sum of the three. If the three are connected in series, they know the frequency of alternating current f, resistor R, inductor L and capacitor C, then the series circuit impedance
;
impedance unit is Europe.
for a specific circuit, the impedance is not constant, but varies with frequency. In resistors,
paul smith uk, inductors and capacitors in series circuit, the impedance of the circuit resistivity generally large. Impedance is reduced to minimum. Inductor and capacitor in parallel circuit, the resonant resistance increases when the maximum, this and the series circuit the opposite.
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