Basic Electrical Terms, Concepts, Formula, And Units Flashcards
Voltage (formula)
W= QE
W= work in Joules Q= charge in Columb E= electric potential or voltage in Volts
Current (formula)
Q= It or dq= idt
Q= charge in columb I= current in Amperes t= time in seconds
Power (formula)
P= VI or P=I²R or P= V²/R
P= power in watts V= voltage in volts I= current in amperes R= resistance in ohms
Resistance (formula)
RA= ρL
R= resistance in Ohms A= cross sectional area in m² ρ= resistivity of a given length and cross sectional area of a certain material, normally measured at 20° C reference temperature in Ω-m L= length in meters
Resistance in drawing process (formula)
RV= ρL² or RA²=ρV
R= resistance in Ohms A= cross sectional area in m² ρ= resistivity of a given length and cross sectional area of a certain material, normally measured at 20° C reference temperature in Ω-m L= length in meters V= volume of wire in m³
Insulation Resistance of an Insulated cable (formula)
2πLR=ρIn(r1/r2)
R= resistance in Ohms r1= bigger radius in meters r2= smaller radius in meters ρ= resistivity of insulator in Ω-m L= length in meters
Temperature effect οn resistance (formula)
R2(T+t1)=R1(T+t2) or R2=R1{1+αt1(t2-t1)}
R1= resistance @ temperature t1 R2= resistance in temperature t2 T= inferred absolute zero temperature α= temperature coefficient of resistance, α(t)=1/(T+t)
A Coulomb is equal to ______ electrons or protons.
1C = 6.25x10¹⁸ electrons or protons
1 watthour is equal to _____ Joules
1Wh = 3600J
1 horsepower is equal to ______ watts
1Hp = 746W
1 mil is equal to _____ inch
1 mil = 0.001 in.
1 CM is equal to ____ square mil
1 CM = π/4 square mil
Anything that occupies space and has mass
Matter
A substance that cannot be decomposed any further by chemical action
Element
Smallest part that an element can be reduced to and still keeping the chemical properties of the element
Atom
Combination of two or more elements
Compound
It is the smallest particle that a compound can be reduced to before it breaks down into its elements.
Molecule
Negatively charged particles that revolve around the nucleus of an atom
Electrons
Mass of an electron
About 9.11x10-³¹ kg
Maximum number of electron in a given shell (formula)
N=2n²
N= total number of electron in a given shell n= nth shell of the atom
Positively charged particles that stay in the nucleus of an atom
Protons
Mass of a proton
1.673x10-²⁷ kg
Particles having no charge
Neutrons
Mass of a neutron
1.675x10-²⁷ kg
The central part of the atom where the protons and neutrons are located at the __________.
Nucleus
Represents the number of electrons and protons of an element
Atomic number
Represents the sum of protons and neutrons of an atom
Atomic mass
Electrons found in the outermost shell or orbit of an atom
Valence electrons
Materials having less than four valence electrons
Conductors
Materials having four valence electrons
Semi-conductors
Materials having more than four valence electrons
Insulators
Unit of electric charge
Coulomb (C)
Unit for electric charge is named after __________.
Charles A. Coulomb (French physicist, 1736-1806)
One electron or proton has a charge of ______ coulombs
1.6x10-¹⁹ C (reciprocal of 6.25x10¹⁸ electrons or protons per charge)
A body is said to be charge if
It has either an excess or deficit of electron from its normal values due to sharing
Any charge has the capability of doing work of moving another charge either by __________ or ____________.
Attraction or repulsion
When a potential difference between two charges forces a third charge to move, the change in motion is called a/an __________.
Electric current (denoted as I)
The capacity to do work
Energy (usually denoted as W)
The net number of electorns moved in the direction of the positive charge depend upon the ________ between the two charges.
Potential difference (denoted as E or V)
Unit of potential difference
Volts (V)
Unit of potential difference is named after ____________.
Alessandro C. Volta (Itallian physicist, 1754-1827)
Who invented the first electric battery?
Alessandro C. Volta¹ & John Stringfellow² (1799 or 1800)
Unit of charge flow
Ampere (A)
Unit of charge flow is named after
Andre M. Ampere (French physicist and mathematician, 1775-1836)
Property of material that opposes or resist the flow of electrons
Resistance (denoted as R)
Unit for resistance
Ohm (Ω)
Practical unit of resistance is named after ________.
Georg S. Ohm (German physicist, 1787-1854)
The amount of change of resistance in a material per unit change in temperature
Specific resistance or resistivity
Area of a circle having a diameter of one mil
CM or circular mil
Resistance of a given length and cross sectional area of a certain material
Resistivity (ρ)
Resisitivity of a material is normally measured at _____ reference temperature.
20°C
The reciprocal of resistance
Conductance (denoted as G)
Unit for conductance
Siemens (S)
When conductors undergo drawing process, the material is assumed negligible (100% efficiency), thus keeping the ________ to be constant all throughout the process.
Volume
For conductors udergoing drawing process, the resistance varies __________ of the length.
Resistance varies directly as the square of the lenght
R2/R1 = (L2/L1)²
Subscript 1= before drawing process
Subscript 2= after drawing process
For conductors undergoing drawing process, the resistance varies ________ of the diameter.
Resistance varies inversely as the fourth power of the diameter.
R2/R1 = (d1/d2)⁴
Subscript 1= before drawing process
Subscript 2= after drawing process
Resistance if all wires generally used in practice of electrical systems ___________ as the temperature increases.
Increases
Ohmic change per degree at some specific temperature
Temperature coefficient of resistance (denoted as α)
Temperature coefficient formula @ temp t (formula)
αt = 1/(T + t)
αt= temperature coeeficient @ temp t T= inferred temperature t= temperature
