1.
ELECTRONICS Electronics Branch of science dealing with devices, circuits and systems that control the flow of electrons in various media, like vacuum, gas, liquid and solid 1.1
Types of Electronic Components Passive Component a device that dissipates power cannot control current and does not generate voltage examples: resistors, capacitors, inductors Active Component a device that does not dissipate power can control current and can do rectification or amplification of voltage can change an energy from one form to another examples: diodes, transistors, tubes, display devices
2.
ATOMIC STRUCTURE 2.1
Substances Atom smallest particle that retains characteristics of element all matter is composed of atoms naturally neutral with equal negative electrons and positive protons Ion an ion is a charged atom negative ion, an atom that received an extra electron positive ion, an atom that gave off an electron ionization, a process of losing and gaining of electrons Element a substance that cannot be decomposed any further by chemical reaction there are around 109 known elements Compound a substance made of two or more elements Page 1 of 10
Molecule basic component of a compound 2.2
Particles of Atom Electron basic quantity of negative electricity valence electrons, the outmost electrons bound electrons, the inner electrons free electrons or conduction electrons, electrons that are free to move charge = -1.602 x 10-19 C Proton basic quantity of positive electricity 1840 times heavier that electron charge = +1.602 x 10-19 C Neutron neutral particle in atom most massive charge = none Mass of Electron, Proton and Neutron melectron
= 9.108 x 10 -28 g
mproton
= 1.672 x 10 -24 g
mneutron
= 1.675 x 10 -24 g
Atomic Number equals the number of protons of an element hydrogen has 1, silicon has 14, germanium has 32, copper has 29 2.3
Bohr Model planetary-like structure of representing an atom an atom having a central nucleus with electrons revolving at certain orbits the nucleus contains protons and neutrons Ne = 2n2
Ne is the maximum number of electrons in orbits, n is 1 for K shell, n is 2 for L shell, n is 3 for M shell, and so on Page 2 of 10
3.
ELECTRICITY Electricity flow of charges in a circuit lightning is a natural electricity can be produced by chemical reaction or by conversion of mechanical energy or simply by friction 3.1
Open and Close Circuit Open Circuit the conducting path has an infinite resistance the current is zero but voltage is maximum Short Circuit the conducting path has zero resistance the current is excessive but the voltage is zero
3.2
Electrical Quantities Charge (Q) quantity of electrons or protons coulomb (C), unit for electric charge 1 C = 6.25 x 10 18 electrons Electric Current (I) flow of charges moving in the same direction due to an applied voltage its symbol I stands for intensity of electron flow dc current, flows in only one direction ac current, flows in alternate directions periodically ampere (A), unit for current 1A=1C/1s Voltage (V) the same as potential difference or electromotive force force that is used to move electrons Page 3 of 10
dc voltage, with only one polarity ac voltage, the polarity alternates volt (V), unit for voltage 1V=1J/1C=1W/1A Resistance (R) opposition to the electric current limits the amount of current in the circuit ohm ( ), unit for resistance 1
=1V/1A
Conductance (G) reciprocal of resistance, G = 1/R siemen (S), unit for conductance, formerly mho 1 S = 1 A / V = (1
) -1
Power (P) rate of doing work or transferring an energy watt (W), unit for electric power 1W=1J/1s 1 hp = 746 W Work (W) energy dissipated or generated in a circuit joule (J), unit for work or energy electronvolt (eV), unit for energy on a single electron 1 eV = 1.6 x 10 -19 J Impedance (Z) combination of resistance and reactance in ac circuit phase angle between the voltage and current ranges between -900 to +900 Admittance (Y) reciprocal of impedance Reactance (X) resistance offered by capacitive and inductive elements Susceptance (B) reciprocal of reactance Page 4 of 10
3.3
Basic Formula Q = It V = IR = IZ P = VI = I2R = V2/R W = Pt = QV G = 1/R :=2 f T = 1/f B = 1/X Z2 = R2 + X2 < = tan-1 X/R pf = cos < = R/Z Y = 1/Z where
B, susceptance f, frequency G, conductance I, current P, power pf, power factor Q, charge R, resistance t, time T, period V, voltage W, work or energy X, reactance Y, admittance Page 5 of 10
Z, impedance C, angular frequency in radians / second D, phase angle 3.4
AC Sine Wave VPP = 2 VP VAC = VRMS = VEFF = 0.707 VP VDC = VAVE = 0.637 VP Form Factor = VRMS/VAVE VPP = peak-to-peak voltage VP = peak voltage VAC = ac, rms or effective voltage VDC = dc or average voltage
3.5
Electrical Wires Circular Mil (cmil) Unit for cross-sectional area of wires A(cmil) = [ d(mil) ]2 1 cmil, area of wire with 1-mil diameter 4 cmil, area of wire with 2-mil diameter, and so on American Wire Gage (AWG) standard gage to indicate wire sizes gage number ranges from 1 to 40 AWG # 40, wire with smallest diameter AWG # 22, wire for electronic circuits AWG # 14, for house wiring
3.6
Protection Devices Fuse protection from overload during short circuit condition excessive current melts the fuse element slow-blow fuse, melts only on continued overload, used in motor circuit Circuit Breakers Page 6 of 10
short circuit protection with spring as a thermal element spring expands in heat and opens the circuit 4.
MAGNETISM Magnet can attract pices of iron lodestone, a natural magnet alnico, permanent magnet often used in loudspeakers keeper, placed across poles to maintain strength during storage air gap, air space between poles of magnet degaussing, another name for demagnetization Curie temperature, where materials lose magnetism toroid, electromagnet with close magnetic ring core 4.1
Magnetic Quantities Flux (B) the number of available magnetic lines of force maxwell (Mx), cgs unit for flux weber (Wb), SI unit for flux 1 Mx = 1 magnetic line 1 Wb = 1 V· 1 s = 1 x 10 8 Mx Flux Density (C) specifies the amount of electromagnetic lines per unit area gauss (G), cgs unit for flux density tesla (T), SI unit for flux density 1 G = 1 Mx / 1 cm2 1 T = 1 Wb / 1 m2 Magnetomotive force (mmf) amount of magnetizing force or magnetic potential coercive force, needed to reduce flux density to zero domain, arrangement of atoms under mmf gilbert (Gb), cgs unit for mmf ampere-turn (At), SI unit for mmf Page 7 of 10
1 At = 1.26 gB Magnetic Field Intensity (H) amount of magnetomotive force per unit of length oersted (Oe), cgs unit for magnetic field intensity ampere-turn per meter, SI unit for H 1 Oe = 1 Gb / 1 cm 1 At/m = 0.00126 Oe 4.2
Permeability Permeance (F) property that concentrates the magnetic flux reluctance, reciprocal of permeance retentivity, ability to retain magnetism 4.2.1
Materials According to Permeability Ferromagnetic highly attracted to magnets strongly magnetized in the same direction as magnetizing force with very high permeability, from 50 to 5,000 examples: alnico, cobalt, iron, nickel, permalloy, steel, ferrites ferrites, nonmetallic materials but ferromagnetic, like ceramic Paramagnetic slightly attracted to magnets weakly magnetized in the same direction as the magnetizing force with permeability slightly greater than 1 examples: aluminum, chromium, manganese, platinum Diamagnetic slightly repelled by magnets weakly magnetized in opposite direction as the magnetizing force with permeability slightly less than 1 examples: antimony, bismuth, copper, gold, mercury, silver, zinc
4.3
Formula for Magnetic Circuits Page 8 of 10
C=B/A
mmf = IN
H = mmf/L
µ = C/H
mmf = B R
5.
M
- flux density
N
- magnetic flux
A
- area
mmf
- magnetomotive force
I
- electric current
N
- number of turns
H
- magnetic field intensity
mmf
- magnetomotive force
L
- length
µ
- permeability
M
- flux density
H
- magnetic field intensity
mmf
- magnetomotive force
N
- magnetic flux
R
- reluctance
LAWS, THEOREMS, RULES Kirchoff’s Voltage Law It states that the algebraic sum of the voltage sources and voltage drops in any closed path is equal to zero. Kirchoff’s Current Law It states that the sum of the currents entering a node is equal to the sum of currents leaving the same node. Superposition Theorem In a linear, bilateral network having more than one source, the current and voltage in any part of the network can be found by adding algebraically the effect of each source separately. All other sources are killed temporarily; with independent voltage sources shorted and independent current sources opened. Page 9 of 10
Thevenin’s Theorem Any network with two open terminals can be replaced by a single voltage source in series with a single resistance. Norton’s Theorem Any two-terminal network can be replaced by a single current source in parallel with a single resistance. Millman’s Theorem It is a theorem that provides a shortcut for finding the common voltage across any number of parallel branches with different voltage sources. This common voltage equals the sum of currents in parallel branches divided by the sum of conductances in parallel branches. V = QI/QG Coulomb’s Law The force between charges is proportional to the amount of charges, and is inversely proportional to the square of the distance between charges. Faraday’s Law The amount of induced voltage is directly dependent on the number of turns of a coil and on the rate a flux cuts the conductor. Lenz’ Law States that the direction of the induced current produces magnetic field that opposes the action that produced the induced current. Ampere’s Law This is the basic principle of electric motors. It states that any current-carrying conductor located in a magnetic field, at right angles to the lines of force, will be pushed by a force that is directly proportional to the flux density, current, and length of conductor. Left Hand Rule It is used to determine the magnetic polarity. It states that if a coil is grasped with the fingers of the left hand, curled around the coil in the direction of electron flow, the thumb points to the north pole of the coil. Right Hand Motor Rule This is used to determine the rotation of a motor. If the index finger points to the direction of flux, and the middle finger to the direction of electron flow in conductor, then the thumb will point to the direction of the force. Page 10 of 10
