Basics of Electronics

README.md

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 # pcb-guide
+## Basics of Electronics:
+### What is Electric Current?
+An electric current is a flow of electric charge in a circuit. More specifically, the electric current is the rate of charge flow past a given point in an electric circuit. The charge can be negatively charged electrons or positive charge carriers including protons, positive ions or holes.
+### What is Conventional current flow?
+  The conventional current flow is from positive to the negative terminal and indicates the direction that positive charges would flow.
+  
+### What is Electron flow?
+  The electron flow is from negative to positive terminal. Electrons are negatively charged and are therefore attracted to the positive  terminal as unlike charges attract.
+### Effects of current
+  When an electric current flows through a conductor there are a number of signs which tell that a current is flowing.
+  
+##### • Heat is dissipated:  
+  If the current is small then the amount of heat generated is likely to be very small and may not be noticed. However if the current is larger then it is possible that a noticeable amount of heat is generated. An electric fire is a prime example showing how a current causes heat to be generated. The actual amount of heat is governed not only be the current, but also be the voltage and the resistance of the conductor.
+  
+##### • Magnetic effect: 
+  Another effect which can be noticed is that a magnetic field is built up around the conductor. If a current is flowing in conductor then it is possible to detect this. By placing a compass close to a wire carrying a reasonably large direct current, the compass needle can be seen to be deflect. Note this will not work with mains because the field is alternating too fast for the needle to respond and the two wires (live and neutral) close together in the same cable will cancel out the field.
+The magnetic field generated by a current is put to good use in a number of areas. By winding a wire into a coil, the effect can be increased, and an electro-magnet can be made. Relays and a host of other items use the effect. Loudspeakers also use a varying current in a coil to cause vibrations to occur in a diaphragm which enable the electronic currents to be converted into sounds.
+##### _Unit of Electric Current: ampere, amp_ #####
+#### What is resistance?
+Resistance is the hindrance to the flow of electrons in material. While a potential difference across the conductor encourages the flow of electrons, resistance discourages it. The rate at which charge flows between two terminals is a combination of these two factors.
+##### _Units: ohms_ ##### 
+#### Ohm's Law:
+Ohm's law states that the current flowing in a circuit is directly proportional to the applied potential difference and inversely proportional to the resistance in the circuit.
+#####  _Ohm's Law formula_ ##### 
+                                           V=IR
+##### Where: #####
+    V = voltage expressed in Volts
+    I = current expressed in Amps
+    R = resistance expressed in Ohms
+#### Resistivity definition: ####
+The resistivity of a substance is the resistance of a cube of that substance having edges of unit length, with the understanding that the current flows normal to opposite faces and is distributed uniformly over them.
+The electrical resistivity is the electrical resistance per unit length and per unit of cross-sectional area at a specified temperature.
+##### _Resistivity formula / equation:_ ##### 
+The resistivity of a material is defined in terms of the magnitude of the electric field across it that gives a certain current density. It is possible to devise an electrical resistivity formula.
+ρ=EJ
+##### _Where:_ ##### 
+    ρ is the resistivity of the material in ohm metres, Ω⋅m
+    E is the magnitude of the electric field in volts per metre, V⋅m^-1
+    J is the magnitude of the current density in amperes per square metre, A⋅m^-2
+#### Capacitors
+Capacitors are simple passive device that can store an electrical charge on their plates when connected to a voltage source.
+##### _Standard Units of Capacitance_ #####  
+• Microfarad  (μF)   1μF = 1/1,000,000 = 0.000001 = 10-6 F
+• Nanofarad  (nF)   1nF = 1/1,000,000,000 = 0.000000001 = 10-9 F
+• Picofarad  (pF)   1pF = 1/1,000,000,000,000 = 0.000000000001 = 10-12 F
+##### _SI unit: farad_ ##### 
+##### _Other units: μF, nF, pF_ ##### 
+#### Inductance:
+Inductance is used in many areas of electrical and electronic systems and circuits. Components can be in a variety of forms and may be called by a variety of names: coils, inductors, chokes, transformers, . . . Each of these may also have a variety of different variants: with and without cores and the core materials may be of different types.
+##### There are two ways in which inductance is used: #####
+##### Self-inductance:
+Self-inductance is the property of a circuit, often a coil, whereby a change in current causes a change in voltage in that circuit due to the magnetic effect of caused by the current flow. It can be seen that self-inductance applies to a single circuit - in other words it is an inductance, typically within a single coil. This effect is used in single coils or chokes.
+##### Mutual-inductance: 
+Mutual inductance is an inductive effect where a change in current in one circuit causes a change in voltage across a second circuit as a result of a magnetic field that links both circuits. This effect is used in transformers.
+##### _SI unit : henry, H_ ##### 
+#### Voltage: 
+he standard unit of potential difference and electromotive force in the International System of Units(SI), formally defined to be the difference of electric potential between two points of a conductor carrying a constant current of one ampere, when the power dissipated between these points is equal to one watt.
+##### _Units: Volt_ ##### 
+#### Power:
+Electric power is the rate, per unit time, at which electrical energy is transferred by an electric circuit. It is the rate of doing work.
+##### _Formula:_ ##### 
+W=V I
+                                                 I = Q/t
+##### Where:
+    W = power in watts
+    V = potential in volts
+    I = current in amps
+    Q = charge in coulombs
+    t = time in seconds
+##### _Unit: watt_ ##### 
+#### watt:
+The watt is the SI unit of power defining the rate of energy conversion and it is equivalent to one joule per second.
+The watt can be defined according to the application:
+##### • Electrical definition of the watt:
+One watt is the rate at which work is done when a current of one ampere, I of current flows through a network which has an electrical potential difference of one volt,
+                                                   V. W = V I
+##### • Mechanical definition of the watt:  
+One watt is the rate at which work is done when the velocity of an object is held constant at one metre per second against constant opposing force of one newton.
+