# Electrical and Electronic Topics

#### (electricity has become one of the most significant areas of study in the world)

electric current
An electric current consists of charged particles moving through a conductor usually consisting of electrons.

The electrons in some atoms; such as, copper and aluminum, are free to move and to jump from one atom to another and such materials are known as conductors.

Other materials; such as, wood, do not contain as many moving electrons, and so they are called insulators and when a material is neither completely a conductor nor an insulator, it is called a semiconductor.

When an electric current moves continuously in one direction, it is called a direct current and when the current fluctuates rapidly back and forth, it is called an alternating current.

Alternating current is used in almost all worldwide household wiring today while direct current is commonly seen in battery-operated devices.

electrical and electronics engineers
Being one of the largest branches of engineering, these specialities design and develop electrical and electronic equipment and products.
• They work with power generation and transmission; machinery controls; lighting and wiring for buildings, automobiles, and aircraft; computers; radar; communications equipment; missile guidance systems; and consumer goods; such as, television sets and appliances.
• They may specialize in communications, computers, or power distribution equipment, or in a subdivision; such as, aviation electronic systems or in the research, development, and design of new products.
electrical multimeters
Either as analogue or digital meters, they are used to measure electrical units, including voltage, resistance, and current.

The units on a multimeter include direct current volts (DCV), alternating current volts (ACV), ohms (?), and direct current milliamps (DCmA).

electricity-measuring units
1. The amp, short for ampere, is the amount of electric current flowing in a wire.

The electric current is measured in electrons per second.

2. The ohm is a measure of resistance to current.

The higher the resistance at a given voltage, the less current flows. Higher resistance can be obtained by using thinner wires or by using materials which are less efficient conductors.

3. The volt is a measure of the potential energy of the source or the "pressure" pushing electrons through the wire.
4. A watt is a unit of electric power or the speed at which an electric current can function.

Electric energy is expressed in units called watt-hours, which is what is usually referred to in everyday speech when someone says "watts".

A 100-watt light bulb, that operates for one hour, uses one watt-hour and electricity which is used in a home is normally metered in kilowatt-hours, or thousands of watt-hours.

electronics
See the multitudes of electronic terms that are located at this site.
electrostatics
All matter is composed of atoms, which in turn are composed of subatomic particles.
• Many of those particles consist of a property called a "charge", which may be positive or negative.
• The most familiar charged particles are electrons, which posses a negative charge; and protons, that posses a positive charge.
• Electric particles with the same charges repel one another; while particles with the opposite charges attract each other.
• Normally, the electrons and protons in an atom are in balance, and the atom has no net charge.
• Charles Coulomb, French physicist famous for his discoveries in the field of electricity and magnetism; formulated Coulomb's Law (1736-1806), determined that positive and "negative electric charges" attract one another and that "like charges repel" each other with a force which is proportional to the amount of charge and diminishes with the square of the distance.

This is called Coulomb's Law in honor of Charles Coulomb, and the electric charge is now measured in units called coulombs.

• When negative and positive charges are separated, an electrical potential energy is created which is called voltage; which represents the amount of work it would take to move the charge between two points.
• When separated electric charges can move, they create an electric current and the current is the rate of flow of the electric charge.
nonmetallic cloak
Development of a process using identical glass resonators made of chalcogenide glass, a type of dielectric material (one that does not conduct electricity).

In computer simulations, the cloak made objects hit by infrared waves disappear from human view; such waves were approximately one micron or one-millionth of a meter long.

The invisibility cloak uses metamaterials, which are artificial materials having properties that do not exist in nature, made of tiny glass resonators arranged in a concentric pattern in the shape of a cylinder.

Spokes of a concentric configuration produce the magnetic resonance required to bend light waves around an object, making it invisible.

Metamaterials, which use small resonators instead of atoms or molecules of natural materials, incorporate the boundary between materials science and electrical engineering.

—Compiled from excerpts as seen in
"Now You See It, Now You Don’t — an Invisibility Cloak Made of Glass";
Michigan Tech News by Jennifer Donovan,
Michigan Technological University, July 23, 2010.