Module 1: Introduction to Matter, Energy, and Direct Current Flashcards
Ammeter
an instrument for measuring the amount of electron flow in amperes
Ampere
the basic unit of electrical current
Anode
a positive electrode of an electrochemical device (such as a primary or secondary electric cell) toward which the negative ions are drawn
Attraction
the force that tends to make two objects approach each other. Attraction exists between two unlike magnetic poles (North and South) or between two unlike static charges (plus and minus)
Battery
a device for converting chemical energy into electrical energy
Battery Capacity
the amount of energy available from a battery. Battery capacity is expressed in ampere-hours
Bleeder Current
the current through a bleeder resistor. In a voltage divider, bleeder current is usually determined by the 10 percent rule of thumb
Bleeder Resistor
a resistor which is used to draw a fixed current
Branch
an individual current path in a parallel circuit
Cathode
the general name for any negative electrode
Cell
a single unit that transforms chemical energy into electrical energy. Batteries are made up of cells
Charge
represents electrical energy. A material having an excess of electrons is said to have a negative charge. A material having a deficiency of electrons is said to have a positive charge.
Circuit
the complete path of an electric current
Circular Mil
an area equal to that of a circle with a diameter of 0.001 inch. It is used for measuring the cross-sectional area of wires
Combination Circuit
a series-parallel circuit
Conductance
the ability of a material to conduct or carry an electric current. It is the reciprocal of the resistance of the material, and is expressed in mhos or siemans
Conductivity
ease with which a substance transmits electricity
Conductor
(1) a material with a large number of free electrons.
(2) a material which easily permits electric current to flow
Coulomb
a measure of the quantity of electricity. One coulomb is equal to 6.28x10^18 electrons
Coulomb’s Law/Law of Electric Charges/Law of Electrostatic Attraction
charged bodies attract or repel each other with a force that is directly proportional to the product of their individual charges and inversely proportional to the square of the distance between them.
CPR
Cardio-Pulminary Resuscitation
Cross-Sectional Area
the area of a ‘slice’ of an object. When applied to electrical conductors, it is usually expressed in circular mils
Current
the flow of electrons past a reference point. The passage of electrons through a conductor. Measured in amperes
Dead Short
a short circuit having minimum resistance.
Dielectric Field
the space between and around charged bodies in which their influence is felt. Also called Electric Field of Force or an Electrostatic Field
Direct Current
an electric current that flows in one direction only
Domain Theory
a theory of magnetism based upon the electron-spin principle. Spinning electrons have a magnetic field. If more electrons spin in one direction that another, the atom is magnetized.
Dry Cell
an electrical cell in which the electrolyte is not a liquid. In most dry cells the electrolyte is in the form of a paste
Efficiency
The ration of output power to input power, generally expressed as a percentage
Electric Current
the flow of electrons
Electrical Charge
Symbol Q, q. Electric energy stored on or in an object. The negative charge is caused by an excess of electrons; the positive charge is caused by a deficiency of electrons
Electrochemical
the action of converting chemical energy into electrical energy
Electrode
The terminal at which electricity passes from on medium into another, such as in an electrical cell where the current leaves or returns to the electrolyte
Electrolyte
a solution of a substance which is capable of conducting electricity. An electrolyte may be in the form of either a liquid or a paste.
Electromagnet
an electrically excited magnet capable of exerting mechanical force, or of performing mechanical work
Electromagnetic
the term describing the relationship between electricity and magnetism. Having both magnetic and electric properties.
Electromagnetic Induction
the production of a voltage in a coil due to a change in the number of magnetic lines of force (flux linkages) passing through the coil
Electron
the elementary negative charge that revolves around the nucleus of an atom
Electron Shell
a group of electrons which have a common energy level that forms part of the outer structure (shell) of an atom
Electrostatic
pertaining to electricity at rest, such as charges on an object (static electricity)
Element
a substance, in chemistry, that cannot be divided into simpler substances by any means ordinarily available
EMF
(Electromotive Force) the force which causes electricity to flow between two points with different electrical charges or when there is a difference of potential between the two points. The unit of measurement in volts
Energy
the ability or capacity to do work
Equivalent Resistance
(R_eq) a resistance that represents the total ohmic values of a circuit component or group of circuit components. Usually drawn as a single resistor when simplifying complex circuits
Ferromagnetic Material
a highly magnetic material, such as iron, cobalt, nickel, or alloys, make up these materials
Field of Force
a term used to describe the total force exerted by an action-at-a-distance phenomenon such as gravity upon matter, electric charges acting upon electric charges, magnetic forces acting upon other magnets or magnetic materials
Fixed Resistor
a resistor having a definite resistance value that cannot be adjusted
Flux
in electrical or electromagnetic devices, a general term used to designate collectively all the electric or magnetic lines of force in a region
Flux Density
the number of magnetic lines of force passing through a given area
Gas
one of the three states of matter having no fixed form or volume. (Steam is a gas)
Graph
a pictorial presentation of the relation between two or more variable quantities, such as between an applied voltage and the current it produces in a circuit
Ground Potential
zero potential with respect to the ground or earth
Horsepower
the English unit of power, equal to work done at the rate of 550 foot-pounds per second. Equal to 746 watts of electrical power
Horseshoe Magnet
a permanent magnet or electromagnet bent into the shape of a horseshoe or having a U-shape to bring the two poles near each other
Hydrometer
an instrument used to measure specific gravity. In batteries hydrometers are used to indicate the state of charge by the specific gravity of the electrolyte
Induced Charge
an electrostatic charge produced on an object by the electric field that surrounds a nearby object
Induced Current
current due to the relative motion between a conductor and a magnetic field
Induced Electromotive Force
the electromotive force induced in a conductor due to the relative motion between a conductor and a magnetic field
Induced Voltage
see Induced Electromotive Force
Induction
the act or process of producing voltage by the relative motion of a magnetic field across a conductor
Infinite
(1) extending indefinitely, endless
(2) boundless, having no limits
(3) an incalculable number
Insulation
(1) a material used to prevent the leakage of electricity from a conductor and to provide mechanical spacing or support to protect against accidental contact.
(2) Use of material in which current flow is negligible to surround or separate a conductor to prevent loss of current.
Insulator
(1) material of such low conductivity that the flow of current through it can usually be neglected. (device having high-electric resistance, used for supporting or separating conductors so as to prevent undesired flow of current from the conductors to other objects
Inversely
inverted or reversed in position or relationship
Ion
an electrically charged atom or group of atoms. Negative ions have an excess of electrons; positive ions have a deficiency of electrons
Ionize
to make an atom or molecule of an element lose an electron, as by X-ray bombardment, and thus be converted into a positive ion. The freed electron may attach itself to a neutral atom or molecule to form a negative ion
Junction
(1) the connection between two or more conductors
(2) the contact between two dissimilar metals or materials, as is in a thermocouple
Kilo
a prefix meaning one thousand
Kinetic Energy
energy which a body possesses by virtue of its motion
Kirchhoff’s Laws
(1) the algebraic sum of the currents flowing toward any point and the current flowing from that point in an electric network is zero.
(2) the algebraic sum of the products of the current and resistance in each of the conductors in any closed path in a network is equal to the algebraic sum of the electromotive forces in the path
Law of Magnetism
like poles repel; unlike poles attract
Lead-Acid Cell
a cell in an ordinary storage battery, in which electrodes are grids of lead containing an active material consisting of certain lead oxides that change in composition during charging and discharging. The electrodes or plates are immersed in an electrolyte of diluted sulfuric acid.
Line of Force
a line in an electric or magnetic field that shows the direction of the force
Liquid
one of the three states of matter which has a definite volume but no definite form (water is a liquid)
Load
(1) a device through which an electric current flows and which changes electrical energy into another form.
(2) power consumed by a device or circuit in performing its function
Local Action
a continuation of current flow within an electrical cell when there is no external load. Caused by impurities in the electrod
Magnetic Field
the space in which a magnetic force exists
Magnetic Poles
the section of a magnet where the flux lines are concentrated; also where they enter and leave the magnet
Magnetism
the property possessed by certain materials by which these materials can exert mechanical force on neighboring masses of magnetic materials; and can cause currents to be induced in conducting bodies moving relative to the magnetized bodies
Matter
any physical entity which possesses mass
Mega
a prefix meaning on million, also Meg
Mho
unit of conductance: the reciprocal of the ohm. Replaced by siemens
Micro
a prefix meaning one-millionth
Milli
a prefix meaning one-thousandth
Negative Electrode
a terminal or electrode having more electrons than normal. Electrons flow out of the negative terminal of a voltage source
Negative Temperature Coefficient
the temperature coefficient expressing the amount of reduction in the value of a quantity, such as resistance for each degree of increase in temperature
Network
a combination of electrical components. In a parallel circuit it is composed of two or more branches
Neutral
in normal condition hence neither positive nor negative. A neutral object has a normal number of electrons
Ohm
the unit of electrical resistance. It is that value of electrical resistance through which a constant potential difference of 1 volt across the resistance will maintain a current flow of 1 ampere through the resistance
Ohmic Value
resistance in ohms
Ohm’s Law
the current in an electric circuit is directly proportional to the electromotive force in the circuit. The most common form of the law is E=IR, where E is the electromotive force or voltage across the circuit, I is the current flowing in the circuit, and R is the resistance of the circuit
Open Circuit
(1) the condition of an electrical circuit caused by the breaking of continuity of one or more conductors of the circuit; usually an undesired condition.
(2) a circuit which does not provide a complete path for the flow of current
Parallel Circuit
two or more electrical devices connected to the same pair of terminals so separate currents flow through each; electrons have more than one path to travel from the negative to the positive terminal
Permeability
the measure of the ability of a material to act as a path for magnetic lines of force
Photoelectric Voltage
a voltage produced by light
Pico
a prefix adopted by the National Bureau of Standards meaning 10^-12
Piezoelectric Effect
the effect of producing a voltage by placing a stress, either by compression, expansion, or twisting, on a crystal and, conversely, producing a stress in a crystal by applying a voltage to it
Plate
one of the electrodes in a storage battery
Polarity
(1) the condition in an electrical circuit by which the direction of the flow of current can be determined. Usually applied to batteries and other direct voltage sources.
(2) two opposite charges, on positive and one negative.
(3) a quality of having two opposite magnetic poles, one north and the other south
Polarization
the effect of hydrogen surrounding the anode of a cell which increases the internal resistance of the cell
Potential Energy
energy due to the position of one body with respect to another body or to the relative parts of the same body
Potentiometer
a 3-terminal resistor with one or more sliding contacts, which functions as an adjustable voltage divider
Power
the rate of doing work or the rate of expending energy. The unit of electrical power is the watt
Primary Cell
an electrochemical cell in which the chemical action eats away one of the electrodes, usually the negative electrode
Reciprocal
the value obtained by dividing the number 1 by any quantity
Reference Point
a point in a circuit to which all other points in the circuit are compared
Reluctance
a measure of the opposition that a material offers to magnetic lines of force
Repulsion
the mechanical force tending to separate bodies having like electrical charges or like magnetic polarity
Residual Magnetism
magnetism remaining in a substance after removal of the magnetizing force
Resistance
(1) the property of a conductor which determines the amount of current that will flow as the result of the application of a given electromotive force. All conductors possess some resistance, but when a device is made especially for the purpose of limiting current flow, it is called a resistor.
(2) the opposition which a device or material offers to the flow of current. The effect of resistance is to raise the temperature of the material or device carrying the current.
(3) a circuit element designed to offer a predetermined resistance to current flow
Resistor
the electrical component which offers resistance to the flow of current. It may be a coil of fine wire or a composition rod
Retentivity
the ability of a material to retain its magnetism
Rheostat
(1) a resistor whose value can be varied.
(2) a variable resistor which is used for the purpose of adjusting the current in a circuit
Schematic Circuit Diagram
a circuit diagram in which component parts are represented by simple, easily drawn symbols. May be called a schematic.
Schematic Symbols
a letter, abbreviation, or design used to represent specific characteristics or components on a schematic diagram
Secondary Cell
a cell that can be recharged by passing a current through the cell in a direction opposite to the discharge current
Series Circuit
an arrangement where electrical devices are connected so that the total current must flow through all the devices; electrons have one path to travel from the negative terminal to the positive terminal
Series-Parallel Circuit
a circuit that consists of both series and parallel networks
Shelf Life
the period of time that a cell or battery may be stored and still be useful
Shielding
a metallic covering used to prevent magnetic or electromagnetic fields form effecting an object
Short Circuit
a low resistance connection between two points of different potential in a circuit, usually accidental and usually resulting in excessive current flow that may cause damage
Siemans
the new and preferred term for mho
Solid
one of the three states of matter which has definite volume and shape (Ice is a solid)
Source Voltage
the device which furnishes the electrical energy used by a load
Specific Gravity
the ratio between the density of a substance and that of pure water at a given temperature
Static Electricity
stationary electricity that is in the form of a charge. The accumulated electric charge on an object
Switch
a device to connect, disconnect, or change the connections in an electrical circuit
Tapped Resistor
a wire-wound, fixed resistor having one or more additional terminals along its length, generally for voltage-divider applications
Temperature Coefficient
the amount of change of resistance in a material per unit change in temperature
Terminal
an electrical connection
Thermocouple
a junction of two dissimilar metals that produces a voltage when heated
Tolerance
(1) the maximum error or variation from the standard permissible in a measuring instrument.
(2) a maximum electrical or mechanical variation from specifications which can be tolerated without impairing the operation of a device
Total Resistance
(R_T) the equivalent resistance of an entire circuit.
Unidrectional
in one direction only
Valence
the measure of the extent to which an atom is able to combine directly with other atoms. It is believed to depend on the number and arrangement of the electrons in the outermost shell of the atom
Valence Shell
the electrons that form the outermost shell of an atom
Variable Resistor
a wire-wound or composition resistor, the value of which may be changed
Volt
the unit of electromotive force or electrical pressure. One volt is the pressure required to send 1 ampere of current through a resistance of 1 ohm
Voltage
(1) the term used to signify electrical pressure. Voltage is a force which causes current to flow through an electrical conductor.
(2) the voltage of a circuit is the greatest effective difference of potential between any two conductors of the circuit
Voltage Divider
a series circuit in which desired portions of the source voltage may be tapped off for use in equipment
Voltage Drop
the difference in voltage between two points. It is the result of the loss of electrical pressure as current flows through a resistance
Watt
the practical unit of electrical power. It is the amount of power used when one ampere of dc flows through a resistance of one ohm
Wattage Rating
a rating expressing the maximum power that a device can safely handle
Watt-Hour
a practical unit of electrical energy equal to one watt of power for one hour
Weber’s Theory
a theory of magnetism which assumes that all magnetic material is composed of many tiny magnets. A piece of magnetic material that is magnetized has all of the tiny magnets aligned so that the north pole of each magnet points in one direction
Wire
a solid or stranded group of solid, cylindrical conductors having low resistance to current flow, with any associated insulation
Work
the product of force and motion
