AREA III - Farm Electrification Flashcards
One of the most versatile and widely used forms of energy.
a. Wind
b. Electricity
c. Water
d. Geothermal
b. Electricity
Clouds driven by strong winds can gather huge electrostatic charges which are released to the earth in the form of lightning.
a. Chemical Action
b. Adiabatic reaction
c. Friction between moving objects
d. Cyclonic motion of objects
c. Friction between moving objects
Certain types of crystals produce a voltage when subjected to pressure.
a. Magnetism
b. Thermoelectricity
c. Photoelectricity
d. Piezoelectricity
d. Piezoelectricity
Voltage is produced when the junction of two unlike metals is heated.
a. Magnetism
b. Thermoelectricity
c. Photoelectricity
d. Piezoelectricity
b. Thermoelectricity
A material that uses the principle of thermoelectricity.
a. Thermal Conductors
b. Heat Insulator
c. Thermolinks
d. Thermocouples
d. Thermocouples
Solar or photo cells convert radiant energy to electrical energy.
a. Magnetism
b. Thermoelectricity
c. Photoelectricity
d. Piezoelectricity
c. Photoelectricity
Produces a voltage by operating on the principle of electromagnetic induction.
a. Magnetism
b. Thermoelectricity
c. Photoelectricity
d. Piezoelectricity
a. Magnetism
Smallest portion into which an element can be subdivided without losing its physical and chemical properties
a. Molecules
b. Atom
c. Carbon
d. Particle
b. Atom
Outermost electrons
a. Negatively-charged Electrons
b. Protons
c. Positively- charged Electrons
d. Valence Electrons
d. Valence electrons
if an object contains more number of total electrons than the total protons
Negatively charged
if an atom contains fewer number of total electrons than the total protons
Positively charged
the amount of electrical charge on a single electron
Elementary charge unit (ECU)
used to measure quantity of electric charge; approximately equal to 6.24 x 10^18 ECU.
Coulomb (C)
Defined as the rate at which electrical charge flows
a.
b.
c.
d.
Current
Causes electric charge to flow in an electrical system having potential difference
Electromotive force (emf)
Ability of a material to resist the flow of electrical charge when subjected to a given potential difference
Electrical Resistance
property of a material to oppose the flow of electric current
Resistivity
materials having an intermediate resistance to electron flow
Semiconductors
materials which has low resistance to electron flow
Conductors
materials which has high resistance to electron flow
Insulators
States that the current flowing in a circuit varies directly with the electrical pressure and inversely with the opposition
Ohm’s law
States that the sum of the current in a node must be equal to zero
Kirchhoff’s current law
The net voltage around a close circuit is zero
Kirchhoff’s voltage law
The common unit of electric power
Watt
The common unit of electric resistance
Ohm
Power factor for electric motors
between 0.6 to 0.8
Power factor for heaters, electric ranges and incandescent lamps.
1
The common unit of electric energy consumption
watt-hour (Wh)
the voltage across each resistor is directly proportional to the ratio of its resistance to the total series resistance of the circuit
Voltage divider
the current divides in inverse proportion to the resistances of the individual parallel elements
Current divider
TRUE or FALSE. it is impossible to view a very complicated circuit in terms of much simpler equivalent source and load circuits
FALSE
States that any network composed of ideal voltage and current sources, and of linear resistors, may be represented by an equivalent circuit consisting of an ideal voltage source in series with an equivalent resistance.
Thevinin’s theorem
States that any network composed of ideal voltage and current sources, and of linear resistors, may be represented by an equivalent circuit consisting of an ideal current source in parallel with an equivalent resistance.
Norton’s theorem
Characterized by non-variant current flow in one direction at all times
Direct Current (DC)
Characterized by an alternating flow of in two directions
Alternating Current (AC)
When voltage and current are in phase, all the power is __________
Positive
It is “watt-less” and does no useful work.
Reactive power
property to oppose current change
Inductance
The amount of electric charge that a capacitor receives for each volt of applied potential
Capacitance
Power factor improvement can be accomplished on what way?
addition of series or
parallel-connected capacitors.
This material had the ability to attract bits of
iron.
lodestones (Fe3O4)
First magnets
magnetite or
“lodestones” (Fe3O4)
lines of force surrounding a permanent magnet or a moving charged particle.
Magnetic fields
Quantity of magnetic field force or “push”; also known as magnetic potential difference
Magnetomotive force (mmf)
It is Analogous to electric voltage (emf).
Magnetomotive force (mmf)
quantity of total field effect or “substance” of the field; analogous to electric current.
Magnetic flux
amount of field force (mmf) distributed over the length of the electromagnet.
Magnetic field strength (intensity)
amount of magnetic field flux concentrated in a given area
Magnetic flux density
The opposition to magnetic field flux through a given volume of space or material
Reluctance
Measure of a material’s acceptance of magnetic flux
Permeability
Describes that the electric field due to electric charges can be derived by Coulomb’s Law.
Gauss’s law for electricity
states that the net magnetic flux through any (real or imaginary) closed surface is zero.
Gauss’ law for magnetism
Describes the production of magnetic fields not only by electric currents but by changing electric field as well
Ampere’s law
Describes the production of electric fields as a result of
changing magnetic fields
Faraday’s law of induction
Voltage induced by a changing magnetic flux
induced emf
current produced during electromagnetic induction
induced current
A generator that produces unidirectional current
DC generator
also called alternator, produces alternating current
AC generator
3-wire, 3-phase system will deliver how many times as much power as a 2-wire, single-phase system?
1.73 times
A device that transfers energy from one electric circuit to another without change in frequency and usually (but not always) with a change in voltage.
Transformer
The primary winding has more turns than the secondary.
Step-up transformer
The primary winding has fewer turns than the secondary.
Step-down transformer
States that the induced voltage in a coil is always in a direction so as to oppose the effect which is producing it.
Lenz’s law
Refers to the portion of electric conductors that extends from the service entrance to an outlet or a certain group of outlets.
Branch circuit
Type of branch circuit for table lamps, radios, television and other portable appliances.
Lighting and general-purpose circuits
Type of branch circuit for portable appliances in the kitchen, dining area and laundry.
Small appliance circuits
Type of branch circuit for ranges, air conditioners, water heaters, water pumps, furnaces, and dishwashers.
Special purpose circuits
Electrical conductors which are 8 mm2 (AWG No. 8) or smaller in size.
Wires
Electrical conductors which are larger than the wires.
Cables
Meaning of AWG
American Wire Gauge
1 mil is equal to how many inches?
0.001 in
It is useless for many actual calculations involving true area.
circular mil
Grounding of current-carrying portions of a system
System grounding
Grounding of equipment not intended to be at a voltage potential different from the earth
Equipment grounding
What is he resistance of the human body when dry?
about 500,000 Ω
What is he resistance of the human body when wet?
about 300 Ω
Amount of voltage can cause sufficient current to be fatal
30 V
the use of colors of conductor covers in the wiring connections
Polarizing
It is always the ‘neutral wire’
White wire
‘hot’ conductors
Red or black wires
Grounding wire
Green wire
Overcurrent devices of which a portion is destroyed when interrupting the circuit
Fuses
Device designed to open a circuit automatically on a
predetermined overload current without damage to itself
circuit breaker
The best location for indoor type distribution center
Position closest to the
equipment having the largest wattage rating
The best location for outdoor type distribution center
Nearest to the
electrical load center
The best location for pole type distribution center
located at the electrical load center of the
farmstead
Three criteria to consider for the selection of wires for feeder lines
(a) size to carry current.
(b) size of wire to prevent excessive
voltage drop (Allowable voltage drop = 2%).
(c) type and location adapted to
surroundings
It constitutes only a small portion of the electromagnetic spectrum
Light
It involves the procedure of dividing the room into zones.
zonal cavity method
