Unit 33: Electrical Principles and Wiring Materials
reverse (positive) polarity (RP)
DC current flowing in the opposite direction from straight polarity; to reverse the direction of current.
service entrance panel
a box with fuses or circuit breakers where electricity enters a building.
short circuit
a condition that occurs when electricity flows back to its source too rapidly and blows fuses, burns wires, and drains batteries.
electromagnet
a core of magnetic material surrounded by a coil of wire through which an electric current is passed to magnetize the core.
transformer
a device that converts high voltage from high-power lines to 230 volts for home and farm installations; device used to step current up or down.
ground-fault circuit interrupter (GFCI)
a device that cuts off the electricity if even very tiny amounts of current leave the normal circuit.
meter
a device that measures electricity, gas, or liquid that passes through a system.
generator
a device that produces direct current.
magnetism
a force that attracts or repels iron or steel.
electricity
a form of energy that can produce light, heat, magnetic force, and chemical changes.
turbine
a high-speed rotary engine driven by water, steam, or other gases.
ohm
a measure of the resistance of a material to the flow of electrical current.
permanent magnet
a piece of iron or steel that holds its magnetism.
volt-ohm-milliampere meter (VOM meter)
a popular combination meter used in electronics.
rod
a round cylindrical piece of metal.
circuit breaker
a switch that trips and breaks the circuit when more than a specified amount of current passes through it.
electrical metallic tubing (EMT)
a type of bendable conduit in which electrical wires are encased.
entrance head
a waterproof conduit connection where an electrical entrance cable is connected to a building.
service drop
an assembly of electrical wires, connectors, and fasteners used to transmit electricity from a transformer to a service entrance panel.
open circuit
an electrical circuit in which there is at least one place where current cannot flow.
circuit
an electrical source and wires connected to a light, heater, or motor.
conductor
any material that will permit electrons (electricity) to move through it.
resistance
any tendency of a material to prevent electrical flow.
magnetic field
area around an iron core or electric wire influenced by the presence of magnetism.
nonmetallic sheathed cable
cable composed of copper or aluminum wires covered with paper, rubber, or vinyl for insulation and protection.
positive (hot) wires
conductors with black, red, or blue insulation that carry current to an appliance.
neutral wires
conductors with white insulation that carry current from an appliance back to the source.
alternator
device that produces alternating electrical current but usually equipped with diodes to change current to direct current.
branch circuits
electrical wiring, switches, and outlets that extend out from a service entrance panel.
north pole
end of a magnet opposite the south pole.
south pole
end of magnet opposite the north pole.
armored cable
flexible metal sheath with individual wires inside.
fluorescent light
light tube that glows as a result of electricity flowing through gases.
magnetic flux
lines of magnetic force that occur in patterns between poles of a magnet.
voltage drop
loss of voltage as electricity travels through a wire.
field
magnetic force around an electric wire or iron core.
grounding
making an electrical connection between a piece of equipment and the earth.
insulator
material that provides great resistance to the flow of electricity.
conduit
metal tube with individual insulated wires inside.
kilo-
one thousand
poles
opposite ends of a magnet
fuse
plug or cartridge containing a strip of metal that melts when more than a specified amount of current passes through it.
strands
small wires placed with others to form bundles to improve flexibility and conductivity.
filament
special metal element in a vacuum that produces light when electricity flows through it.
attraction
the action of two magnets that pull together when opposite poles are placed near each other.
repulsion
the action of two magnets that push away from each other when like poles are placed near each other.
shock
the body's reaction to an electric current.
commutator
the part of a motor that changes the flow of current at appropriate times.
Ohm's Law
the relationship between electric current (I), electromotive force (E), and resistance (R): E=IR.
armature
the rotating part of a motor. Also the iron core portion of a magneto.
ampere (A) (amp)
the unit of measure for amperage.
volt (V)
the unit of measure for voltage.
watt (W)
the unit of measure for wattage.
kilowatt-hour
the use of 1,000 watts for one hour.
watt-hour
the use of one watt of electricity for one hour.
milliampere
thousandth of an ampere