Theme 2: Energy and the Environment Background Material

Basic Electrical Concepts

Electricity
The term "electricity" is very confusing because of the way that it is used in our language. In reality, the word "electricity" should be confined to a field of science rather than as an actual term.

Electric Current

In metals, electric current is the slow flow of charged particles (electrons) within a metal conductor. It is the flowing motion of matter, not of energy. Electrons flow very slowly and that can be measured in centimetres per minute rather than at the speed of light. It is the energy in the circuit, not the electrons, which moves very fast.

Electric current "Regions of positive or negative charge, such as those at the terminals of a battery, foce electrons through a conductor. The electrons move from negative charge toward positive. Originally, current was thought to flow from positive to negatie this is so-called "conventional current"." From "Ultimate Visual Dictionary of Science," Stoddart 1998.

When the electrons at one point in the circuit are pushed, electrons in the entire circuit are forced to flow, instantly spreading energy through the circuit. This happens even though the electrons move very slowly. The flow of current through a conductor enables the transfer of energy in a light bulb.

Electrical Energy

Electrical energy is composed of electromagnetic fields which do not travel along with individual electrons.

Even though the electrons do not move very quickly, the electromagnetic energy moves very fast on the outside of the conductor.

Simple circuit. Copyright 1991, The National Academy of Sciences. Reproduced with permission from Electric Circuits, National Sciences Research Center.

In a simple circuit involving a battery, two wires and a light bulb, the charges vibrate in the wire, the negative electrons move in one direction while the positive metallic core moves simultaneously in the other direction.

Electromagnetic energy is produced by the vibrations of the charged particles (negative and positive). The electromagnetic energy flows along both wires and is converted into another form of energy (light and heat) inside the light bulb.

Electromagnetic energy is defined as the energy emitted from vibrating charges inside the circuit. The heat is defined as the energy produced by vibrating masses of charges. Since both the electrons in the outer edge of atoms and the vibrating core of the wire have mass and charge, their vibrations cause both heat and electromagnetic energy.

Conductor

A conductor is any material that contains movable electric charges. In a pure copper wire, the geometry of the positive and negative charges is such that most of the electromagnetic energy is caused by the freely moving electrons. Although some heat is produced, the copper wire conducts the electricity with little or no resistance.

Filament

Lightbulb with filament Copyright 1991, The National Academy of Sciences. Reproduced with permission from Electric Circuits, National Sciences Research Center.

The filament of a light bulb is made of a metal (tungsten) that does not have the same geometry of positive and negative charges as a copper wire. If the arrangement of atoms in a wire is not orderly, collisions occur sending charged particles in all directions. The collisions result in the production of heat while diminishing the overall electromagnetic energy moving along the entire conductor.