Electrical Elements Flashcards
What does a wire gauge represent?
the diameter of the entire wire, bigger gauge number, smaller diameter and vice versa
What are the common gauge numbers used in households?
10AWG - 5.261mm^2
12AWG - 3.309mm^2
14AWG - 2.081mm^2
Superconductor is also known as?
Cryogenic conductor
What material is the best conductor of electricity?
Silver, due to most number of free electrons per unit volume
which metals are the best conductors of electricity
Pure silver
Pure copper
Pure gold
Aluminum
What are wire-wound resistors?
Uses metal alloys that are independent of temperature like manganin and constantan, and have an inductive property
What are thin film resistors
Deposited thin metal(Ceramic Metal) on an insulating support, Has High Resistance, Has no Reactive property
What are carbon composition resistors?
low wattage fixed type made from carbon, Its size is proportional to the power it can handle
What is a rheostat?
variable resistor with only two terminals, used in high power and high voltage, wire-wound(has inductive property)
What is potentiometer
variable resistor used for low power and low current application, has 3 terminals
Resistors color code
1st significant, Second Significant, multiplier, tolerance,
Black Black 0 Boys Brown 1 Respect Red 2 Our Orange 3 Young Yellow 4 Girl Green 5 But BLue 6 Violeta Violet 7 Goes Gray 8 White White 9
What does the reliability (5th) band in a resistor indicate?
Reliability (in percent of failure per 1000 hours of use)
It is the fundamental source of electrical energy developed through the conversion of chemical or solar energy
Cell
Combination of two or more cells
Battery
These are not rechargeable cells, AND DO NOT HAVE RESISTANCE
Primary Cell
These are rechargeable cells AND HAVE RESISTANCE
Secondary Cells
Two common rechargeable cells
Lead-Acid used in automobiles
Nickel-Cadmium used in calculators/tools/photoflash units
Carbon-zinc (Leclanche): Classification and output voltage
Primary/1.5V designed for 70 degrees Farenheit operation
Zinc Chloride: Classification and output voltage
Primary/1.5V Heavy Duty type
Manganese Dioxide (alkaline): Classification and output voltage
Primary or Secondary/ 1.5V has low internal resistance
Mercuric Oxide: Classification and output voltage
Primary/1.35V
Silver Oxide: Classification and output voltage
Primary 1.5V
Lead Acid: Classification and output voltage
secondary 2.1V
Ni-Cd: Classification and output voltage
Secondary 1.25V
Nickel-Iron(Edison Cell): Classification and output voltage
Secondary 1.2V
Nickel-Metal hydride: Classification and output voltage
Secondary 1.2V, does not suffer memory effect
Silver-Zinc: Classification and output voltage
Secondary 1.5V
Silver Cadmium : Classification and output voltage
Secondary 1.1V
Battery Life expression
Battery Life(Hr)=Ampere-Hour rating(Ah)/Amperes Draws
Also called as Crowfoot cell/gravity cell/wet cell used in operating telegraphs and door bells
Daniel Cell
Also called as galvanic Cell, Named after Luigi Galvani
Voltaic Cell
Primary Cell with high output voltage, long shelf life, low weight and small and can provide 10x more energy
Lithium Cell
Very good power to weight ratio, often found in high end laptop
Lithium-ion battery
Used in electric vehicles
Metal-chloride battery
Other name for a capacitor
Condenser
Unit of capacitance is named after?
Michael Faraday
What is the reciprocal of capacitance?
Elastance, unit is daraf
What is Gauss Theorem
The total electric flux extending from a closed surface is equal to the algebraic sum of the charges inside the closed surface
Gauss Theorem mathematical Expression
ψ = Q
Wb(Unit of flux) = C(unit of charge)
ψ - # Electric Flux Lines
Q - Charges inside an enclosed surface
Electric Flux Density Formula
D=ψ/Area
where: ψ=total flux, Mx or Wb
A=Area, cm^2 or m^2
1 Tesla= 1Wb/m^2
1 Gauss = 1 Maxwell/cm^2
Electric Field Intensity Formula
E=F/Q
F= Newtons,
Q=Charge, Coulomb
in capacitors:
E=V/d
where V=voltage, d=plate separation
First law of Electrostatics
unlike charges attract each other while like charge repel each other
Second law of elecrostatics
the force of attraction or repulsion between charges is directly proportional to the product of the two charges but inversely proportional to the square of distance between them
Second law of statics mathematical formula
F = kq1q2/r^2
k=1/(4πεoεr)
εo=absolute permittivity, shift constant 32
What is permittivity?
It is the ratio of electric flux density to the electric field strength
ε=D/E (in Farads/m)
relative permittivity (εr) of teflon
2.0
relative permittivity (εr) of paper, paraffined
2.5
relative permittivity (εr) of mica
5.0
relative permittivity (εr) of transformer oil
4.0
It is the voltage required per unit length to establish conduction in a dielectric
Dielectric Strength or breakdown voltage
Dielectric strength of Air
75 V/mil
OR
3 x 10^6 (V/m)
Dielectric strength of Barium-strontium titanite(ceramic)
75 V/mil
OR
3 x 10^6 (V/m)
Dielectric Strength of transformer oil
400 V/mil
Formula for the energy stored in a capacitor
Wc=1/2*CV^2 or Q^2/2C
What is the electrical definition of capacitance?
Charge per unit volt
C=Q/V
Q=charge
V=Voltage
Formula for capacitance based on physical construction
C=(n-1)*(εA/d)
n=number of parallel plates
ε=permittivity
A=plate area
d=distance bet. plates
Series Capacitor’s total capacitance
Ct = 1 / ( {1 / C1} + {1 / C2} + ….)
Total charge in a series capacitor
Qt=Q1=Q2=Q3
Identical capacitors in series total capacitance
Ct=C/n
Total capacitive reactance on series capacitors
Xct=Xc1+Xc2+Xc3..
Parallel Capacitor Total capacitance
Ct= C1 + C2 + C3
Parallel Capacitor identical capacitors capacitance
Ct = nC
Parallel Capacitor total charge
Qt=Q1+Q2+Q3…
Parallel Capacitor capacitive reactance
Xct = 1 / ( {1/Xc1{ + {1/Xc2} + {1/Xc3} )
capacitance of parallel-plate capacitor (with multiple dielectrics in between)
C = εoA / ( [d1/εr1] + [d2/εr2] + [d3/εr3] )
d1,d2,d3 - dielectric thickness within the parallel plates
εr1, εr2, εr3 - Relative Permittivity of the dielectrics
Cylindrical capacitor formula
C = [ (εr*l) / (41.4log(b/a)) ] x10^-9
a=inner diameter of single core cable conductor
b=outer diameter
l=length of the cylindrical capacitor
Capacitance of an isolated Sphere
C=4πε*r
r=radius of isolated sphere
Capacitance of concentric sphere, out sphere is grounded
C=4πε(ab/(b-a))
a=inner radius
b-outer radius
Capacitance of concentric sphere, inner sphere is grounded
C=4πε*b^2/(b-a)
a=inner radius
b-outer radius
It is a measure of the ability of a coil to oppose any change in current through the coil. and store energy in the form of magnetic field
Self Inductance/inductance
Formula of inductance in terms of physical dimensions
L=(μ)n^2A/l
μ=permeability of the core, H/m
N=number of turns
A=area of core, m^2
l-mean length of the core
Formula of inductance in terms of electrical definition
L= Hd(Φ)/di
Energy stored by an inductor
Wl=0.5L(I^2)
What is faraday’s law
The voltage induced across a coil of wire equals the number of turns in the coil times the rate of change of magnetic field
Einductor = Nd(Φ)/dt = Ldi/dt
What is lenz’s law?
An induced voltage effect is always such as to oppose the cause that produced it
Lenz’s law mathematical expression
Einductor = - N*d(Φ)/dt
Series inductors without mutual inductance
Lt=L1+L2+L3..
Series inductors with mutual inductance
M=k*sqrt( L1 * L2 )
Lt(aiding) = L1 + L2 + 2M Lt(opposing) = L1 + L2 - 2M
k-coupling coefficient
k = 0 if minimum(Blocked by Dielectric)
k = 1 if maximum(Uses Iron Core)
Parallel inductors total inductance, aiding
Lt(aiding)=(L1*L2 - M^2) / (L1 + L2 - 2M)
Parallel inductors total inductance, opposing
Lt(opposing)=(L1*L2 - M^2) / (L1 + L2 + 2M)
Inductance of long coil
L=(μ)N^2*A/l
Inductance of short coil
L=(μ)N^2*A/(l+.45d)
d - diameter of short coil
Inductance in Toroidal coil with rectangular cross section
L=(μ)(N^2h / 2π) * ln (d2 / d1)
h=thickness, m
d2,d1=outer and inner diameters respectively
L - in μH
Inductance of Circular Air core
L=0.07(RN)^2/(6R+9l+10b)
R=d/2+b/2 d=core diameter,in b=coil buildup,in l = coil thickness, in L - in μH
Inductance of magnetic core coil, no air gap
L = 0.012N^2(μ)A /lc
A - Area in cm^2
lc - magnetic path length (cm)
L - in μH
Inductance of magnetic core coil, air gap
L = 0.012N^2*A /(lg + lc/(μ))
A - Area in cm^2
lc - magnetic path length (cm)
lg - gap length(cm)
L - in μH
The unit of electrical power is named after>
James Watt
Equivalent power (in watts) of 1 HP
1HP=746W
Millman’s Theorem
the voltage across the parallel combination is the ratio of the algebraic sum of currents to the internal conductance
Power transfer efficiency
n=Rl/(Rl+Rsource)x100%
Inferred Absolute Zero Temperature of Copper
T(iazt) = -234.5 °C
Inferred Absolute Zero Temperature of Silver
T(iazt) = -243 °C
When a Conductor is cooled to the Inferred Absolute Zero Temperature, its resistance is __________
zero
Resistivity of Copper (ρ20 in R = ρL/A)
ρ20 = 1.7 x 10^-8 Ω-meters
Resistivity of Silver (ρ20 in R = ρL/A)
ρ20 = 1.5 x 10^-8 Ω-meters
Resistivity of Gold (ρ20 in R = ρL/A)
ρ20 = 2.4 x 10^-8 Ω-meters
Resistivity of Aluminum (ρ20 in R = ρL/A)
ρ20 = 2.6 x 10^-8 Ω-meters
Thermistors are usually used as ______
Sensors
Thermistors are either _____ or ______
PTC, NTC
In a Light Dependent Resistor, its resistance is (Directly/Inversely) Proportional to the illumination on the device
Inversely
When does the resistance of a Light Dependent resistor reach maximum value?
When Completely Dark
What do you call the maximum resistance of a Light Dependent Resistor?
Dark Resistance
In a Voltage Dependent Resistor, its resistance is (Directly/Inversely) Proportional to the Voltage Across the device
Inversely
Voltage Dependent Resistors are usually used for _________
Circuit Protection
The Cross Sectional Area of a conductor assumed by the unit of Circular Mil looks like a _____
Square ¯_(ツ)_/¯
CM = d^2
d - diameter of cable
The Cross Sectional Area of a conductor assumed by the unit of Square Mil looks like a ______
Circle ¯_(ツ)_/¯
SM = (π/4)CM
= (π/4)d^2
d - diameter of cable
Mil is short for ______
Milli-inch (1 x 10^-3)
When 4th Band of a resistor has no color, what is the Tolerance%? And the tolerance Letter Designation?
+- 20% (M)
When 4th Band of a resistor has the color Brown, what is the Tolerance%? And the tolerance Letter Designation?
+- 1% (F)
When 4th Band of a resistor has the color Red, what is the Tolerance%? And the tolerance Letter Designation?
+- 2% (G)
When 4th Band of a resistor has the color Green, what is the Tolerance%? And the tolerance Letter Designation?
+- 0.5% (D)
When 4th Band of a resistor has the color Blue, what is the Tolerance%? And the tolerance Letter Designation?
+- 0.25% (C)
When 4th Band of a resistor has the color Violet, what is the Tolerance%? And the tolerance Letter Designation?
+- 0.1% (B)
When 4th Band of a resistor has the color Gold, what is the Tolerance%? And the tolerance Letter Designation?
+- 5% (J)
When 4th Band of a resistor has the color Silver, what is the Tolerance%? And the tolerance Letter Designation?
+- 10% (K)
When 4th Band of a resistor has the color Gray, what is the Tolerance%? And the tolerance Letter Designation?
+- 0.05% (A)
When 5th Band of a resistor has the color Brown, what is the Reliability?
1%
When 5th Band of a resistor has the color Red, what is the Reliability?
0.1%
When 5th Band of a resistor has the color Orange, what is the Reliability?
0.01%
When 5th Band of a resistor has the color Yellow, what is the Reliability?
0.001% (MOST RELIABLE)
When the 3rd Band of a resistor is Gold, What is the Multiplier used?
x 10^-1
When the 3rd Band of a resistor is Silver, What is the Multiplier used?
x 10^-2
When the 3rd Band of a resistor is Pink, What is the Multiplier used?
x 10^-3
The property of a battery that determines how efficient its quantity of storage is
Ampere-Hour (AH) efficiency
Formula for AH Efficiency(η)
η(AH) = AH(discharge) / AH(charge) η(AH) = I(d)*t(d) / I(c)*t(c)
I(d) and I(c) - Discharging/Charging Current
t(d) and t(c) - Discharging/Charging time
The property of a battery that determines how efficient its storage of Energy is
Watt-Hour Efficiency (WH)
Formula for WH(Watt-Hour) Efficiency(η)
η(WH) = WH(discharge) / WH(charge)
η(WH) = P(d)t(d) / P(c)t(c)
η(WH) = [ V(d)I(d)t(d) ] / [ V(c)I(c)t(c) ]
but η(AH) = I(d)t(d) / I(c)t(c)
———————————————
Therefore: η(WH) = η(AH) * (V(d) / V(c))
———————————————
V(d) and V(c) - Discharging/Charging Voltage
P(d) and P(c) - Discharging/Charging Power
I(d) and I(c) - Discharging/Charging Current
t(d) and t(c) - Discharging/Charging time
What does Temperature resistance coefficient of a material describe?
When temperature increases by 1 °C, the resistance increases by (Temperature resistance coefficient) Ohms
Temperature resistance coefficient (α20) of:
Gold
3.7 x 10^-3 ( /°C)
Temperature resistance coefficient (α20) of:
Silver
3.8 x 10^-3 (/°C)
Temperature resistance coefficient (α20) of:
Copper
3.93 x 10^-3 ( /°C)
Temperature resistance coefficient (α20) of:
Aluminum
4 x 10^-3 ( /°C)
Temperature resistance coefficient (α20) of:
Nichrome
0.4 x 10^-3 (/°C)
Temperature resistance coefficient (α20) of:
Manganin
0.03 x 10^-3 ( /°C)
Temperature resistance coefficient (α20) of:
Constantan
0.008 x 10^-3 ( /°C)
Relative Permittivity (εr) of rubber
3
Relative Permittivity (εr) of Pyrex
5.6
Dielectric Strength (V/m) of Teflon
60 x 10^6 (V/m)
Dielectric Strength (V/m) of Rubber
27.55 x 10^6 (V/m)
Dielectric Strength (V/m) of Paper
16 x 10^6 (V/m)
Dielectric Strength (V/m) of Mica
197 x 10^6 (V/m)
Dielectric Strength (V/m) of Pyrex
14 x 10^6 (V/m)
Capacitor Color Coding
Same as Resistance color coding
Although, for 4th Band Tolerance : Green is 5% in capacitors, not like 0.5% in resistors Grey is 80%-20% in capacitors White is 10% in capacitors Red is 2% in capacitors yellow is 3% in capacitors
(No reliability)
When reading capacitance values, the unit represented by a colored/numbered code is in ___________
PICO farads (pF)
Capacitor Number Coding
Capacitor Nimber Coding contain 4 characters:
Char. 1 and 2, are the 1st and 2nd digit of capacitance value
Char. 3 is the multiplier
Char 4 is the Letter Designation for Tolerance(Same as Resistor)
Capacitor Number Coding:
When 3rd Char is equal to 0, the multiplier used for the capacitance is:
1 pF
Capacitor Number Coding:
When 3rd Char is equal to 1, the multiplier used for the capacitance is:
10
Capacitor Number Coding:
When 3rd Char is equal to 2, the multiplier used for the capacitance is:
100
Capacitor Number Coding:
When 3rd Char is equal to 3, the multiplier used for the capacitance is:
1000
Capacitor Number Coding:
When 3rd Char is equal to 4, the multiplier used for the capacitance is:
10,000
Capacitor Number Coding:
When 3rd Char is equal to 5, the multiplier used for the capacitance is:
100,000
Capacitor Number Coding:
When 3rd Char is equal to 6 or 7, the multiplier used for the capacitance is:
N/A
Capacitor Number Coding:
When 3rd Char is equal to 8, the multiplier used for the capacitance is:
0.01
Capacitor Number Coding:
When 3rd Char is equal to 9, the multiplier used for the capacitance is:
0.1
Alternative Formula for Mutual Inductance(Given aiding and opposing inductance)
M = (Lta - Lto) / 4
Lta -Total aiding Inductance
Lto - Total opposing Inductance
Inductance of Rectangular Air core
L = 0.07*(CN)^2 / (1.908C + 9l +1 0b)
C= d + Y + 2b d=core hole length,in Y=core hole width, in b=coil buildup,in l = coil thickness L - in μH
Inductor Color Coding
Same as Resistor( 1st, 2nd, Multiplier, Tolerance)
What is the unit that represents the value of a Color Coded Inductor?
MICRO Henrys (μH)