Electrical Fundamentals Flashcards
Name three requirements for producing an induced voltage
- Magnetic Field
- Conductor
- Relative motion between the two
A Force moving through a distance is defined as:
Work
The capacity to do work is defined as:
Energy
Terms used to indicate the amount of something
Base units
The symbol for work
W
The symbol for energy
W
The base unit for work
Joule (J)
The base unit for energy
Joule (J)
Force x Distance =
Work
The base unit for force
newton (approximately 0.2248 pounds)
The base unit for distance
meter (approximately 39.4 inches)
1 newton-meter =
1 joule
Formula for expressing efficiency (as a percentage)
useful energy out / useful energy in times (x) 100
The smallest particle of a substance that still has all of its characteristics is called a:
molecule
a molecule consists of
2 or more atoms
matter composed of a single type of atom is called
an element
when different kinds of atoms combine chemically they form
compounds
The three major particles of an atom are
electron, proton and neutron
The center of an atom is called a
nucleus
The first shell of an atom can contain a maximum of _____ electrons
Two
The second shell of an atom can contain a maximum of _____ electrons
Eight
What is the maximum number of electrons that can occupy the third shell of an atom?
18
What is the maximum number of electrons that can occupy the forth shell of an atom
32
The electrons in the outermost shell of an atom are called
valence electrons
Why are electrons capable of doing work?
All electrons possess energy. The possess energy because they have weight and they are moving
Valence electrons that have been temporarily separated from an atom are called
free electrons
A valence electron is freed from its atom when:
energy is added to the atom.
An atom with a positive or negative charge is called
an ion
The base unit of charge is a:
coulomb
The symbol for charge is:
Q
The abbreviation for coulomb is:
C
The movement of charged particles in a specified direction is the definition for
Electric current
The symbol for current is:
I
The symbol I was chosen because early scientists focused on the Intensity of electricity in a wire
current that travels in the same direction all the time is called:
direct current (DC)
The process of emitting electrons from a heated surface is called:
thermionic emission
The base unit of current
ampere (coulombs per second)
1 coulomb = (x) electrons
6.25 x 10 to the 18th power
The electric pressure that causes current to flow
voltage
The symbol for voltage
V
energy in motion
kinetic energy
energy at rest
potential energy
the base unit of voltage
volt (joules per coulomb)
List the 5 ways to produce voltage
Mechanical energy (generator) Chemical energy (battery) Heat energy (thermocouple) Pressure energy (piezoelectric crystal) Light energy (solarvoltaic cells)
The opposition to current flow
resistance
materials that offer little resistance to current flow
conductors
materials that offer high resistance to current flow
insulators
the sharing of valence electrons
covalent bonding
materials that have no resistance to current flow
superconductors
materials that are neither good conductors nor good insulators
semiconductors
the base unit of resistance
ohm
what 4 factors determine the resistance of an object?
1) Type of material
2) The length of the material
3) The cross sectional area of the material
4) The temperature of the material
The change in resistance corresponding to a change in temperature is known as
temperature coefficient of resistance
Give the formula for the relationship of resistance to length, cross-sectional area and resistivity of a material
Resistance (R) = resistivity (K) X length (L) / area (A)
R = KL/A
Materials with no free electrons are called:
insulators
Semiconductors have ____ free electrons
four
The characteristic resistance of a material is known as
resistivity
The rate of doing work or using energy
power
The base unit of power
watt or joule per second (J/s)
Give the formula for the relationship between power, energy and time
Power (P) = energy (W) / time (t)
P = W/t
Give the formula for efficiency as it relates to power
% eff. = P-out / P-in X 100
1 horsepower = ____ watts
746
a drawing that uses only symbols to show how components are connected together is called a
schematic diagram
A meter that measures only one quantity is called a:
panel meter
cells that are not rechargeable are called
primary cells
cells that are rechargeable are called
secondary cells
the capacity of a cell or battery is expressed in
ampere-hours (Ah)
a lead acid cell produces about _____ volts
2.1
What is the chemical composition of the positive plate in a charged battery
lead peroxide (PbO2)
What is the chemical composition of the negative plate in a charged lead acid battery
lead (Pb)
What is the chemical composition of the electrolyte in a charged lead acid battery
dilute sulfuric acid (H2SO4)
When a lead acid battery is overcharged water from the electrolyte is converted into:
hydrogen gas and oxygen gas
The ratio of the weight of a substance to the weight of water is the definition for
specific gravity
What is the specific gravity range for a fully charged lead acid cell?
1.21 to 1.28
The typical automotive battery is fully charged at a specific gravity of
1.26
A lead acid cell is considered discharged when the specific gravity drops below
1.12
