# Basic electronic concepts and Formula

[Current] [voltage] [resistance] [Ohm's law] [Power] [Load] [circuit] [EMF] [cycles] [frequency] [capacitor] [capacitance] [inductance] [inductive] [Impedance] [Phase ] [phase]

Current: directional movement called the charge current. Circuit, the common current I expressed. Two kinds of DC and AC current points. Does not change with time is called the magnitude and direction of the DC current. Magnitude and direction of the current changes with time is called the exchange. Current unit is safe (A), also commonly milliamps (mA) or microamperes (uA) do units. 1A = 1000mA, 1mA = 1000uA.

Current can be measured with a meter. Measuring the time that the ammeter in series with the circuit, to select the ammeter pointer near full-scale deflection. This prevents excessive current damage meter.

Voltage: the river was able to flow because there is water level difference; the charge was able to flow because there is the potential difference. Potential difference is voltage. Voltage is the reason for the formation of the current. In the circuit, the voltage U is used. Voltage unit is volt (V), also commonly millivolts (mV) or microvolts (uV) do units. 1V = 1000mV, 1mV = 1000uV.

Voltage can be measured with a voltmeter. Measuring the time that the voltmeter in parallel on the circuit, to select the voltmeter pointer near full-scale deflection. If the voltage on the estimated size of the circuit do not come out, the first with a large range, after a rough measurement with a suitable range. This prevents excessive voltage from being damaged due to a voltmeter.

Resistance: current through the circuit and caused hinder part of the energy consumed is called resistance. R represents the resistance used. Unit of resistance is Europe (Ω), also commonly kilohms (kΩ) or megohms (MΩ) made units. 1kΩ = 1000Ω, 1MΩ = 1000000Ω. Resistance of the conductor by the conductor material, the cross-sectional area and length of the decision.

You can use a multimeter ohm resistance measurements. Measuring time, to select half of the deflection of the meter pointer near ohm. If the resistance in the circuit, the resistance of an iron should open before measuring.
Ohm's law: U is proportional to the voltage of the conductor current I and the ends of the conductors, and the conductor is inversely proportional to the resistance R, i.e

This law is called Ohm's law. If you know the voltage, current, resistance, volume two of the three, you can find the third volume according to Ohm's law,
In AC circuits, Ohm's law also set up, but the impedance of the resistor R should be changed to Z, namely
Power Supply: The other forms of energy into electrical energy are called a power source. The generator can convert mechanical energy into electrical energy; battery can convert chemical energy into electrical energy. Generator, battery power, etc. is called. Through the transformer and rectifier, the AC power into DC power rectifier device called. To provide an electronic device called a signal source. Transistor can be sent the signal amplification; the amplified signal is transmitted again to the back of the circuit to go. Transistor on the back of the circuit can also be seen as a signal source. Rectifier power supply, the power source is sometimes called.

Load: the electrical energy is converted into other forms of energy is called a load device. Motor can convert electrical energy into mechanical energy, able to convert electrical energy into heat resistance, light bulbs can convert electrical energy into heat and light, a speaker can convert electrical energy into sound energy. Motors, resistors, light bulbs, and so is called the load speaker. For the front of the transistor source, it can also be seen as a load.

Circuit: current flow path is called a circuit. The simplest circuit from the power, loads and wires, switches and other components, shown in Figure 1. Circuit connectivity everywhere called pathway. Only pathways, only the current through the circuit. A circuit breaker or called off at the open. Both ends of a part of the circuit is directly connected, so that this part of the voltage becomes zero, is called the short circuit.

EMF: electromotive force is reflected in the power supply to other forms of energy into electrical energy the ability of physical quantities. EMF generated across the power supply voltage. In the circuit, an electromotive force expressed commonly δ. The same unit of electromotive force and voltage units, but also volts.

Power of the force can be used voltmeter. Measuring time, the power to the circuit do not go, measure the voltage with a voltmeter across the power supply, the resulting voltage value can be seen as equal to the power of the force. If the power supply connected to the circuit (Fig. 2), the voltage across the power supply with the voltage meter will be less than the measured power of the force. This is because the power supply has internal resistance. In the closed circuit, the current through the internal resistance r with the internal voltage drop through the resistor R with external foreign pressure drop. Δ equal to the power of the force within the voltage U r and external voltage UR sum, ie δ = U r + UR. Strictly speaking, even if the power is not access circuit to measure the voltage across the power supply, the external circuits become voltmeter voltage meter; the measured voltage is less than the electromotive force. However, since the internal resistance of the voltmeter is large, the internal resistance of the power supply is small; the internal voltage can be ignored. Therefore, the voltage across the power supply is measured by the voltmeter can be considered as equal to the electromotive force.

Worn batteries with a voltage across the battery voltage measurements, and sometimes still relatively high, but do not make the load (radios, tape recorders, etc.) to work after the access circuit. This happens because the internal resistance of the battery is bigger, even more than the resistive load is still large, but still smaller than the internal resistance of the voltmeter. Voltmeter to measure the voltage across the battery when the battery voltage is not within the resistor share large, so the measured voltage voltmeter is still relatively high. But after the battery access circuit, the battery voltage increases the resistance within the share; the share of the load resistor voltage is reduced, and therefore cannot make the switch. In order to judge the old batteries cannot be used, it should be in a load when measuring the voltage across the battery. Some poor performance of the power supply, there is a load and no load power at both ends of the measured voltage difference between the two cases is large, but also because of the internal resistance of the power of a larger cause.

Cycle: The time to complete a full AC desired change is called the cycle, commonly T represents. Period in seconds (s), also commonly milliseconds (ms) or microseconds (us) to make the unit. 1s = 1000ms, 1s = 1000000us.

Cyclical changes in the frequency of the alternating current frequency completed within 1s called the frequency, f represents common. Unit of frequency is hertz (Hz), also commonly kilohertz (kHz) or megahertz (MHz) to make units. 1kHz = 1000Hz, 1MHz = 1000000Hz. AC frequency f T is the reciprocal of the cycle, i.e.,

Capacitance: Capacitance is a measure of the physical charge storage capacity of the conductor. In two mutually insulated conductors, with a certain voltage, this will be stored in a certain amount of power. One conductor is stored with a positive charge; negative charge stored another conductor of equal size. Plus the voltage, the more and more storage capacity. Plus the voltage of the storage battery is directly proportional to their ratio is called the capacitance. If the voltage is represented by U, power represented by Q, the capacitance is represented by C,
The unit of capacitance is France (F), also commonly microfarads (uF) or picofarads (pF) to make units. 1F = 10 6 uF, 1F = 10 12 pF.

Capacitance capacitor tester can measure; you can also use a multimeter to Ohms rough estimate. Ohmmeter red, black and two pen connected capacitors feet were touching the battery inside the ohmmeter will charge the capacitor, the pointer deflection, charging finished, the pointer back to zero. Swap red and black two pen, then will reverse charging capacitor discharge. The greater the capacitance, the pointer deflection is greater. Comparison of the measured capacitance and the capacitance of the deflection of known cases, you can roughly estimate the magnitude of the measured capacitance. In the general electronic circuitry, in addition to the capacity of the tuning circuit and other needs more precise capacitance, the most used interval, bypass capacitors, filter capacitors, etc., do not require accurate capacity capacitor. Thus, a rough estimate ohm capacitance values ​​are meaningful. However, the general odometer Ohms can estimate the magnitude of the larger capacitance values ​​in smaller capacitance value of the resistor is necessary to use a large transistor odometer Ohms to estimate, less than dozens Capacitance measurement slightly law had to use a capacitor tester.

Capacitance: AC is able through the capacitor, but the capacitor on the AC is still hindered. Capacitance impediment called capacitive reactance of AC. Large capacitance, the AC easily through capacitor described large capacity, a small capacitor hindered; high-frequency alternating current, alternating current through the capacitor can be easily described high frequency, the capacitance is also small impediment. Experiments show that the capacitance and inversely proportional to the capacitance, and frequency is inversely proportional. If the capacitive reactance XC represented by the capacitance is denoted by C, f represents the frequency of use, then

Capacitance of the unit is Europe. Know the alternating current frequency f and capacitor C, the capacitance can be calculated from the above formula.
Inductance: Inductance is a measure of electromagnetic induction coil physical ability. Tell a coil passing a current through the coil will produce a magnetic field around the coil magnetic flux through there. Through the coil power, the more the strong magnetic field, the greater the magnetic flux through the coil. Experimental results show that the magnetic flux and pass into the current through the coil is directly proportional to their ratio is called the self inductance, also called inductance. If φ represents the magnetic flux through the coil current is represented by I, the inductance is represented by L, then commissioning and use of instrumentation.
Hang inductor units (H), also commonly millinery (mH) or micrometry (uH) do units. 1H = 1000mH, 1H = 1000000uH.
Inductance: AC can also coils, but the inductor coil of the AC have hindered this obstacle called inductance. Large inductance, alternating current through the coil is difficult, indicating large inductance, the inductance of a large impediment; high-frequency alternating current, alternating current through the coil is difficult, indicating a high frequency inductor is large impediment. Experiments show and inductive reactance is proportional, and frequency proportional. If the inductive reactance represented by XL, L represents the inductance with frequency represented by f,

Inductive reactant of the unit is Europe. Know the AC frequency f and inductance coil L, the inductance can be calculated from the above formula.

Impedance: a circuit having a resistance, inductance and capacitance, the impediment of play is called AC impedance. Z represents the impedance used. Impedance by the resistance, inductance and capacitance composed of three, but it is not a simple sum of the three. If the three are connected in series, and that the frequency of the alternating current f, the resistance R, inductance L and capacitance C, then the impedance of the series circuit.

Impedance unit is Europe.

For a specific circuit, the impedance is not constant, but as the frequency changes. In the resistance, inductance and capacitance of the series circuit, the impedance circuit is generally larger than the resistance. That is, the impedance is reduced to a minimum. In the parallel circuit of inductor and capacitor, the resonance impedance increases to a maximum when, on the contrary, and this series circuit.

Phase: Phase AC reflects the state of the physical quantity at any time. Magnitude and direction of the alternating current is changing with time. For example a sinusoidal alternating current, which formula is i = Isin2πft. i is the instantaneous value of alternating current, I is the maximum value of the alternating current, f is the frequency of alternating current, t is the time. Over time, the alternating current may vary from zero to a maximum value, and change from the maximum to zero and from zero to a negative maximum value, the maximum change from negative to zero as shown in Figure 3 A ,,. In 2πft equivalent trigonometric angles, it reflects the state in which AC power at any time, is increased or the decrease is positive or negative, and so on. So the 2πft called phase, or called phase.
Inductance: AC can also coils, but the inductor coil of the AC have hindered this obstacle called inductance. Large inductance, alternating current through the coil is difficult, indicating large inductance, the inductance of a large impediment; high-frequency alternating current, alternating current through the coil is difficult, indicating a high frequency inductor is large impediment. Experiments show and inductive reactance is proportional, and frequency proportional. If the inductive reactance represented by XL, L represents the inductance with frequency represented by f,

Inductive reactant of the unit is Europe. Know the AC frequency f and inductance coil L, the inductance can be calculated from the above formula.

Impedance: a circuit having a resistance, inductance and capacitance, the impediment of play is called AC impedance. Z represents the impedance used. Impedance by the resistance, inductance and capacitance composed of three, but it is not a simple sum of the three. If the three are connected in series, and that the frequency of the alternating current f, the resistance R, inductance L and capacitance C, then the impedance of the series circuit.

Impedance unit is Europe.

For a specific circuit, the impedance is not constant, but as the frequency changes. In the resistance, inductance and capacitance of the series circuit, the impedance circuit is generally larger than the resistance. That is, the impedance is reduced to a minimum. In the parallel circuit of inductor and capacitor, the resonance impedance increases to a maximum when, on the contrary, and this series circuit.

Phase: Phase AC reflects the state of the physical quantity at any time. Magnitude and direction of the alternating current is changing with time. For example a sinusoidal alternating current, which formula is i = Isin2πft. i is the instantaneous value of alternating current, I is the maximum value of the alternating current, f is the frequency of alternating current, t is the time. Over time, the alternating current may vary from zero to a maximum value, and change from the maximum to zero and from zero to a negative maximum value, the maximum change from negative to zero as shown in
Figure 3 A ,,. In 2πft equivalent trigonometric angles, it reflects the state in which AC power at any time, is increased or the decrease is positive or negative, and so on. So the 2πft called phase, or called phase. Figure 3

If t is equal to zero when, i was not equal to zero, the formula should be changed to i = Isin (2πft + ψ), as shown in Figure 3 b. So 2πft + ψ called phase, ψ called the initial phase, or called the initial phase.

Phase: the same frequency is called the phase difference between two phase AC, or called a difference. Both the same frequency alternating current may be two AC current, AC voltage may be two, and may be two AC electromotive force; this can also be the amount of any two of the three.

For example, applied to the study of the circuit of AC voltage and AC current through this circuit a phase difference. If the circuit is a pure resistance, the AC voltage and current of the current phase difference is equal to zero. That is equal to zero when the AC voltage, AC current is equal to zero, the AC voltage is changed to the maximum, and the AC current is changed to the maximum. This situation is called the same phase, or called in phase. If the circuit containing inductance and capacitance, AC voltage and AC current phase is generally not equal to zero, that is generally different phases, leading to a current or voltage or current leads the voltage.

Applied to the base electrode of the transistor amplifier and the AC voltage outputted from the collector of the AC voltage, which is exactly equal to the phase difference 180 °. This situation is called anti-phase, or called inverted.

Top