Basic Electrical Terms, Concepts, Formula, And Units

Question 1

Voltage (formula)

Answer 1

W= QE

W= work in Joules
Q= charge in Columb
E= electric potential or voltage in Volts

Question 2

Current (formula)

Answer 2

Q= It or dq= idt

Q= charge in columb
I= current in Amperes
t= time in seconds

Question 3

Power (formula)

Answer 3

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

Question 4

Resistance (formula)

Answer 4

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

Question 5

Resistance in drawing process (formula)

Answer 5

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

Question 6

Insulation Resistance of an Insulated cable (formula)

Answer 6

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

Question 7

Temperature effect οn resistance (formula)

Answer 7

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)

Question 8

A Coulomb is equal to ______ electrons or protons.

Answer 8

1C = 6.25x10¹⁸ electrons or protons

Question 9

1 watthour is equal to _____ Joules

Answer 9

1Wh = 3600J

Question 10

1 horsepower is equal to ______ watts

Answer 10

1Hp = 746W

Question 11

1 mil is equal to _____ inch

Answer 11

1 mil = 0.001 in.

Question 12

1 CM is equal to ____ square mil

Answer 12

1 CM = π/4 square mil

Question 13

Anything that occupies space and has mass

Answer 13

Matter

Question 14

A substance that cannot be decomposed any further by chemical action

Answer 14

Element

Question 15

Smallest part that an element can be reduced to and still keeping the chemical properties of the element

Answer 15

Atom

Question 16

Combination of two or more elements

Answer 16

Compound

Question 17

It is the smallest particle that a compound can be reduced to before it breaks down into its elements.

Answer 17

Molecule

Question 18

Negatively charged particles that revolve around the nucleus of an atom

Answer 18

Electrons

Question 19

Mass of an electron

Answer 19

About 9.11x10-³¹ kg

Question 20

Maximum number of electron in a given shell (formula)

Answer 20

N=2n²

N= total number of electron in a given shell
n= nth shell of the atom

Question 21

Positively charged particles that stay in the nucleus of an atom

Answer 21

Protons

Question 22

Mass of a proton

Answer 22

1.673x10-²⁷ kg

Question 23

Particles having no charge

Answer 23

Neutrons

Question 24

Mass of a neutron

Answer 24

1.675x10-²⁷ kg

Question 25

The central part of the atom where the protons and neutrons are located at the __________.

Answer 25

Nucleus

Question 26

Represents the number of electrons and protons of an element

Answer 26

Atomic number

Question 27

Represents the sum of protons and neutrons of an atom

Answer 27

Atomic mass

Question 28

Electrons found in the outermost shell or orbit of an atom

Answer 28

Valence electrons

Question 29

Materials having less than four valence electrons

Answer 29

Conductors

Question 30

Materials having four valence electrons

Answer 30

Semi-conductors

Question 31

Materials having more than four valence electrons

Answer 31

Insulators

Question 32

Unit of electric charge

Answer 32

Coulomb (C)

Question 33

Unit for electric charge is named after __________.

Answer 33

Charles A. Coulomb (French physicist, 1736-1806)

Question 34

One electron or proton has a charge of ______ coulombs

Answer 34

1.6x10-¹⁹ C (reciprocal of 6.25x10¹⁸ electrons or protons per charge)

Question 35

A body is said to be charge if

Answer 35

It has either an excess or deficit of electron from its normal values due to sharing

Question 36

Any charge has the capability of doing work of moving another charge either by __________ or ____________.

Answer 36

Attraction or repulsion

Question 37

When a potential difference between two charges forces a third charge to move, the change in motion is called a/an __________.

Answer 37

Electric current (denoted as I)

Question 38

The capacity to do work

Answer 38

Energy (usually denoted as W)

Question 39

The net number of electorns moved in the direction of the positive charge depend upon the ________ between the two charges.

Answer 39

Potential difference (denoted as E or V)

Question 40

Unit of potential difference

Answer 40

Volts (V)

Question 41

Unit of potential difference is named after ____________.

Answer 41

Alessandro C. Volta (Itallian physicist, 1754-1827)

Question 42

Who invented the first electric battery?

Answer 42

Alessandro C. Volta¹ & John Stringfellow² (1799 or 1800)

Question 43

Unit of charge flow

Answer 43

Ampere (A)

Question 44

Unit of charge flow is named after

Answer 44

Andre M. Ampere (French physicist and mathematician, 1775-1836)

Question 45

Property of material that opposes or resist the flow of electrons

Answer 45

Resistance (denoted as R)

Question 46

Unit for resistance

Answer 46

Ohm (Ω)

Question 47

Practical unit of resistance is named after ________.

Answer 47

Georg S. Ohm (German physicist, 1787-1854)

Question 48

The amount of change of resistance in a material per unit change in temperature

Answer 48

Specific resistance or resistivity

Question 49

Area of a circle having a diameter of one mil

Answer 49

CM or circular mil

Question 50

Resistance of a given length and cross sectional area of a certain material

Answer 50

Resistivity (ρ)

Question 51

Resisitivity of a material is normally measured at _____ reference temperature.

Answer 51

20°C

Question 52

The reciprocal of resistance

Answer 52

Conductance (denoted as G)

Question 53

Unit for conductance

Answer 53

Siemens (S)

Question 54

When conductors undergo drawing process, the material is assumed negligible (100% efficiency), thus keeping the ________ to be constant all throughout the process.

Answer 54

Volume

Question 55

For conductors udergoing drawing process, the resistance varies __________ of the length.

Answer 55

Resistance varies directly as the square of the lenght R2/R1 = (L2/L1)² Subscript 1= before drawing process Subscript 2= after drawing process

Question 56

For conductors undergoing drawing process, the resistance varies ________ of the diameter.

Answer 56

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

Question 57

Resistance if all wires generally used in practice of electrical systems ___________ as the temperature increases.

Answer 57

Increases

Question 58

Ohmic change per degree at some specific temperature

Answer 58

Temperature coefficient of resistance (denoted as α)

Question 59

Temperature coefficient formula @ temp t (formula)

Answer 59

αt = 1/(T + t) ``` αt= temperature coeeficient @ temp t T= inferred temperature t= temperature ```