Delmar's Textbook of Electricity, Section 1, Units 1 - 5

Basic Laws of Magnetism

-Energy is required to create a magnetic field, but not energy is required to maintain a magnetic field. -Unlike poles attract and like poles repel. -Whenever an electric current flows through a conductor, a magnetic field is formed around the conductor,

Joule

1 newton-meter. A Newton is a force of 100,000 dynes, or about 3 1/2 ounces, and a meter is about 39 inches. 1 watt-second.

6 methods of producing electricity

1) Magnetism 2) chemical action 3) pressure 4) heat 5) friction 6) light

5 Electrical Effects

1) magnetism 2)chemical reactions 3) pressure 4) heat 5) light

Horsepower (hp)

550 foot-pounds per second. A foot-pound is the force needed to raise one pound of weight one foot. 746 watts.

Left-hand Rule

When the fingers of the left hand grips the winding in the direction of electron flow, the thumb points to the north magnetic pole.

Short Circuit

When there is is very low resistance as in only the natural resistance of the conductor and a large amount of current would flow.

Resistance

Used to control the flow of electrons.

Complete Path

A closed circuit for electrons to flow through. You must have a power source, conductors, and load.

Thundercloud

A cloud that contains concentrations of both positive and negative charged raindrops

Lightning arrestor

A device for lightning protection. Designed to bleed away the current of a lightning discharge by having a normal high resistance at normal times and a very low resistance when the object is struck.

Lightning rods

A device to help protect an object from lightning bolts. It provides an easy path to ground for current flow. Invented by Benjamin Franklin.

Lightning bolts

A lightning discharge

Grounding Conductor

A low resistance path back to source

Photon

A massless particle of pure energy. Produced when electrons move from one energy level to another.

Semiconductors

A material that is neither a good conductor or a good insulator. Contains 4 valence electrons and as they are heated, their resistance decreases.

Reluctance

A materials resistance to magnetism. Opposite of permeability.

Permeability

A measure of a material's ability to become magnetized. Opposite of reluctance.

Coulomb (C)

A measure of charge. 625 x 10 to the 18

Coercive Force

A measurement of a material's ability to retain magnetism. Also known as retentivity.

Color Code

Used to determine the resistance value, tolerance, and in some cases reliability.

Impedance

Used to replace resistance in AC circuits.

Precipitators

Uses static charges to attract small particles of smoke, dust, and pollen.

Ampere (A)

A quantity of electrons (coulomb) per second. (1C/second=1A) or (I=q/t) Also known as Intensity of current

Selenium

A semiconductor material that changes its conductivity with a change of light intensity. Highly conductive in light and low conductivity in dark.

Element

A substance that cannot be chemically divided into two or more simpler substances.

Negative

A term used to designate lines of force coming inward.

Positive

A term used to designate the lines of force extending outward.

Pot

A variable resistor. Shortened term for potentiometer.

Potentiometer

A variable resistor. Used to adjust current in a circuit to a certain value. Has three terminals.

Electroscope

An early electric instrument that can be used to determine the polarity of the electro-static charge of an object.

Demagnetized

When an object's molecules become disarrayed due to the introduction of an AC source electromagnet. Can also be achieved with impact and heat.

Lightning

An example of natural static electricity

Electrostatic Charges

An excess of electrons (positive) or lack of electrons (negative). This happens to insulators because they are the only materials that can hold the electrons stationary.

Nuisance Static Charges

An unintended build up of static electricity. Happens on car and truck as they move through the air, builds on a person as they walk across the carpet, and occurs is a clothes dryer. Mostly on man-made materials.

Potential Difference

Another term for Voltage

Rheostat

Another term for a variable resistor. Has two terminals.

Matter

Any substance that has mass and occupies space. Made from a combination of atoms.

Atom

Basic building block of the universe. Smallest part of an element. Made of a proton, electron, and neutron.

Static

Not moving or sitting still.

Nucleus

Combination of protons and neutrons at the center of an atom

Molecules

Combinations of atoms to make a compound or substance.

Electron Flow Theory

Current flows from the most negative point in the vicinity to the most positive

Conventional Current Flow Theory

Current flows from the most positive point in a circuit to the most negative

Ferromagnetic

Easily magnetized materials like iron, nickel, cobalt, and manganese.

Valence Electrons

Electrons in the outermost shell of an atom.

Flux Density

English system of measurement to determine magnetic strength.

Wire-Wound Resistors

Fixed resistors that are made by winding a piece of resistive wire around a ceramic core. Generally used when a high-power rating is needed.

Unidirectional

Flow in one direction

Neutral Conductor

Grounded conductor back to source

Magnetomotive Force (mmf)

Term used to describe the total force producing a magnetic flux.

Saturation

When magnetic strength reaches a point where it's strength increases only slightly with an increase of current. Occurs when all the molecules of the magnetic material are in alignment

Tolerance

Indicates the plus and minus limits of resistor's ohmic value.

Useful Static Charges

Intensional static electricity. Can be used in spray paint applications, air filters, as well as copy machines.

Three substances that form natural magnets

Iron, nickel, and cobalt

Lines of Flux

Magnetic force shells surrounding a magnet that repel each other, never cross, and are stronger near the poles of a magnet.

Flux

Magnetic lines of force.

Electromagnets

Magnets that depend on electrical current flow to produce a magnetic field.

Permanent magnets

Magnets that do not require any power source or force to maintain their field.

Conductor

Material that contains 1-3 valence electrons allowing electrons t flow through them easily. Heat causes their resistance to increase.

Paramagnetic

Materials that can be magnetized but not as easily as ferromagnetic. Examples include platinum, titanium, and chromium.

Diamagnetic

Materials that cannot be magnetized. Magnetic lines of force ho around them rather than through them. Examples include copper, brass, and antimony.

Insulators

Materials that resist the flow of energy. Materials that contain 7-8 valence electrons.

Lodestones

Natural magnets. Known by this name because they always align themselves north and south. Also known as "leading stones"

Multi-turn Variable Resistors

Operated by moving the wiper arm with a screw of America number of turns. Generally range from 3 to 10 turns.

Law of Charges

Opposite charges attract and like charges repel.

Metal Glaze Resistors

Resistor made by combining metal with glass. Similar to the metal film resistor.

Carbon Film Resistor

Resistor that is made by coating a ceramic rod with a film of carbon instead of metal.

Variable Resistor

Resistor whose values can be modified over a range.

Metal Film Resistors

Resistors constructed by applying a film of metal to a ceramic rod in a vacuum. Do not change in value with age.

Composition Carbon Resistor

Resistors made from a compound of carbon graphite and a resin bonding material. The proportions determine the value of resistance. Inexpensive.

Voltage Divider

Resistors used to obtain a specific voltage in a circuit.

Fixed Resistors

Resistors with only one oh mic value which cannot be changed.

Bidirectional

Reverses direction of flow at regular intervals

Repulsion

Similar charges such as Positive to positive or negative to negative

Direct Current

Source of electricity that is unidirectional.

Alternating Current (AC)

Source of electricity where the flow is bidirectional.

Ohm's Law

States that it take 1V to push 1A through 1 ohm. E=I x R

Magnetic Domains (Magnetic Molecules)

The additive effect of electrons in a shared valence shell of molecules like iron, nickel or cobalt. They act like small permanent magnets.

British Thermal Unit (BTU)

The amount of heat required to raise the temperature of 1 pound of water 1 degree Fahrenheit.

Residual Magnetism

The amount of magnetism left in an electromagnet after current has stopped.

Volt (V)

The amount of potential necessary to cause 1 coulomb to produce 1 joule of work.

Watt (W)

The amount of power being used in a circuit.

Angle of Declination

The angular difference between true north and magnetic north.

Power

The change of energy from electrical to something else.

Electromotive Force (EMF)

The force that pushes electrons through a wire. Electrical pressure.

Electron Spin Patterns

The idea that an electron spins on its axis making it a tiny permanent magnet.

Attraction

Unlike charges such as positive to negative

Electron

The negative charged part of an atom.

Atomic Number

The number of protons in an element.

Ampere-turns

The number of turns of wire multiplied by the current flow in an electromagnet.

Electron Orbit

The outer shell of an atom. There are multiple orbits.

Neutron

The part of an atom that has no charge

Proton

The positive part of an atom.

Voltage

The potential difference between two points of a conducting wire carrying a constant current of 1 Ampere when the power dissipated between these points is 1 Watt.

Ohm (♎️)

The unit of resistance to current flow. The amount of resistance that allows 1 ampere of current to flow when the applied voltage is 1 volt