Appendix I Glossary - Cont'd -141200437

GROUND POTENTIAL-- Zero potential with

HYSTERESIS LOSS-- The power loss in an iron-core

respect to the ground or earth.

transformer or other ac device as a result of

magnetic hysteresis.

HALF-CELL-- One of the electrodes and its

immediate environment in an electrochemical cell;

INDUCED CURRENT-- Current due to the relative

an electrode and environment arranged for the

motion between a conductor and a magnetic field.

passage of current to another electrode for the

INDUCED ELECTROMOTIVE FORCE-- The

measurement of its electrode potential; when

electromotive force induced in a conductor due to

coupled with another half-cell, an overall cell

the relative motion between a conductor and a

potential develops that is the sum of both half-cell

magnetic field. Also called induced voltage.

potentials.

INDUCED REACTANCE (XL)-- The opposition to

HENRY (H)-- The electromagnetic unit of inductance

the flow of an alternating current caused by the

or mutual inductance. The inductance of a circuit is

inductance of a circuit, expressed in ohms.

1 henry when a current variation of 1 ampere per

INSULATION-- (1) A material used to prevent the

second induces 1 volt. It is the basic unit of

leakage of electricity from a conductor and to

inductance. In radio, smaller units are used, such as

provide mechanical spacing or support to protect

the millihenry (mH), which is one-thousandth of a

against accidental contact. (2) Use of material in

henry (H), and the microhenry

which is

which current flow is negligible to surround or

one-millionth of a henry.

separate a conductor to prevent loss of current.

HERTZ (Hz)-- A unit of frequency equal to one cycle

INTERLOCK-- A device that prevents an action from

per second.

taking place at the desired time, but will allow the

HORSEPOWER (hp)-- The English unit of power,

action when all required conditions are met.

equal to work done at the rate of 550 foot-pounds

ION-- An electrically charged atom or group of atoms.

per second. Equal to 746 watts of electrical power.

Negative ions have an excess of electrons; positive

HOT WIRE METER MOVEMENT-- A meter

ions have a deficiency of electrons.

movement that uses the expansion of a heated wire

JACKING GEAR-- Electric motor-driven device that

to move the pointer of a meter; measures ac or dc.

rotates the turbine shaft, reduction gears, and line

HYDRAULIC ACTUATOR-- A device that converts

shaft at a low speed.

hydraulic pressure to mechanical movement.

KILO-- A prefix meaning one thousand.

HYDROGEN BLISTERING-- The formation of

KINETIC ENERGY-- Energy that a body possesses

blisterlike bulges on or below the surface of a

by virtue of its motion.

ductile metal caused by excessive internal

hydrogen pressure. Hydrogen may be formed

KIRCHHOFF'S LAWS-- (1) The algebraic sum of

during cleaning, plating, corrosion, or cathodic

the currents flowing toward any point in an electric

protection.

network is zero. (2) The algebraic sum of the

products of the current and resistance in each of the

HYDROGEN EMBRITTLEMENT-- Severe loss of

conductors in any closed path in a network is equal

ductility caused by the presence of hydrogen in the

to the algebraic sum of the electromotive forces in

metal; for example, through pickling, cleaning, or

the path.

cathodic protection.

LEAD-ACID CELL-- A cell in an ordinary storage

HYDROMETER-- An instrument used to measure

battery, in which electrodes are grids of lead

specific gravity. In batteries, hydrometers are used

containing an active material consisting of certain

to indicate the state of charge by the specific gravity

lead oxides that change in composition during

of the electrolyte.

charging and discharging. The electrodes or plates

HYSTERESIS-- The time lag of the magnetic flux in

are immersed in an electrolyte of diluted sulfuric

a magnetic material behind the magnetizing force

acid.

producing it, caused by the molecular friction of the

molecules trying to align themselves with the

LINE OF FORCE-- A line in an electric or magnetic

magnetic force applied to the material.

field that shows the direction of the force.

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