Voltage Current Direct Current Alternating Current Ampere Charge Ohm’s Law Resistors Enameled wire 漆包线 Power rating 额定功率 Photoresistor Thermistor Capacitors Inductors Diode Transistors Integrated Circuits Switches Electromechanical Insulator Conductor


the voltage of a single point in an electronic circuit means the difference between the voltage at one point in the circuit and ground.

\[I=V/R V=I*R\]

Kirchhoff’s Current Law, at any point on a circuit, the current flowing into that point must equal the current flowing out Kirchhoff’s Voltage Law, all the voltages between various points around a circuit will add up to zero.

In electronics, power is the rate of conversion of electrical energy to some other form of energy (usually heat). It is measured in Joules of energy per second, which is also known as a watt (W).

\[P = I*V\]

平方平均数 - 维基百科,自由的百科全书


100Ω and 100R both mean a resistor with a resistance of 100 ohms.

I generally keep the following resistor values in stock: 10Ω, 100Ω, 270Ω, 470Ω, 1k, 3.3k, 4.7k, 10k, 100k, and 1M.

The overall resistance of a number of resistors in series is just the sum of the separate resistances.

if there are two resistors R1 and R2 in parallel, then the overall resistance is given by:


most common standards is AWG (American Wire Gauge) mostly used in the US, SWG (Standard Wire Gauge) mostly used in the UK and most logically just the diameter of the wire in mm.

Capacitors and Inductors

Type Of Capacitors

In most cases, for capacitors between 1pF and 1nF use a disc capacitor (陶瓷电容器 Figure 3-6a). For capacitors between 1nF and 1µF use a multilayer ceramic capacitor (MLC;积层陶瓷电容器; Figure 3-6b) and for capacitors above 1µF use an aluminum electrolytic capacitor (铝电解电容器; Figure 3-6c). tantulum electrolytic capacitor (钽电解电容器).

ESR(equivalent series resistance)

a capacitor in J: \(E = (C*V^2)/2\)


Coil of wire

A change in current in one direction in an inductor causes a change in voltage in the opposite direction.

the higher the frequency of the AC, the more the inductor resists the flow of current. So as not to confuse this effect with ordinary resistance, it is called reactance but it still has units of Ω.

\(X = 2\{pi}fL\) X, reactance. f, frequency of the AC. L inductance of the inductor units are the Henry(H).

L depend on number of turns of wire and the wire.

A type of inductor called a choke is designed to let DC pass while blocking the AC part of a signal.


Block the Flow of Current in One Direction

anode cathode rectification Vf,forward voltage Zener diode

forward bias reverse bias


Transistors are used to control the flow of a current. In digital electronics this control takes the form of an on/off action, with the transistor acting as an electronic switch

Bipolar Junction Transistor Darlington Transistor MOSFET Insulated Gate Bipolar Transistor TRIAC(TRIode for alternating current)



Pole Throw

Reed switches

Power supplies