Creating an Electron Highway: Principles of Electricity
Electricity and the Atom
Everything physical is made up of atoms, which are particles that are so small they cannot even be seen by the most powerful of microscopes. However, the atom is also made up of even smaller particles. One particle is the electron, which is actually a small particle of electricity. The amount or quantity of charge this electron holds is the smallest quantity of electricity that exists. The type of electric charge associated with the electron is called negative.

An ordinary atom consists of a central core called a nucleus, and it is around this nucleus that one or more electrons circulate or orbit. This is very similar to the way planets orbit around the sun. The nucleus has an electric charge called positive. In a normal atom, the positive charge of a nucleus is always equal to the sum of the negatively charged electrons around that nucleus.

Drawing of nuclei and orbiting electrons

One important fact about these two “opposite” kinds of electricity is that they are strongly attracted to each other. Also there is a strong opposing force between two charges of the same kind. The positive nucleus and the negative electrons are attracted to each other; however, two negatively charged electrons will be repelled from each other and so will two positively charged nuclei. This is very similar to the like poles of different magnets opposing each other.

Drawing of magnets poles and flux lines opposing each other

In a normal atom the positive charge on the nucleus is exactly balanced by the negative charges on the electrons. However, it is possible for an atom to lose one of its electrons. When that happens, the atom has less negative charge than it should. The result is called an “ionized” atom and, in this case, it is a positive ion. An atom can also pick up an extra electron, and this atom would then be a negative ion. A positive ion will attract any stray electron that is near, or it can attract a single electron or the extra electron from any negative ion in the vicinity. This is the way that electrons travel from one atom to another. This movement of electrons from atom to atom is called electric current. The amount of current flow is measured in Amperes or Amps. This is very similar to flowing water. The water molecules represent electrons, and the movement of water in a stream represents current flow.

Drawing of several adjacent atoms that are passing electrons in a common direction simulating electron or current flow.

The amount of electric current is measured by determining the total amount of electrons flowing past any point in the circuit. If we use the water flow as an example, it would be how much water travels past a single point on the shore of a stream.

Conductors and Insulators
All materials are made up of atoms that have the following electrical characteristics. Some atoms give up their electrons very easily when attracted by an outside force, and some do not give up their electrons at all even when the outside electric force is very strong. Materials that give up their electrons easily are conductors because they will let their electrons move from atom to atom. The following list gives examples of materials that are conductors.

• Metals
• Carbons
• Acids
• Water

Wire is made from metal that has high conductive properties. Gold is one of the best conductors in the metal family. Gold is also very expensive; consequently, it would cost far too much to use gold as the conductor in wire to create current paths or circuits. That is why copper is commonly used as the material that wires is usually made from. It is far cheaper than gold and it has very excellent conductive properties.

Materials that do not permit their electrons to move from atom to atom are called insulators. This list gives some examples of common materials that are insulators.

• Dry Air
• Wood
• Porcelain
• Glass
• Rubber

Large amounts of electricity are very dangerous. Heat is produced as electrons’ flow in a conductive material. The human body is composed of materials that are capable of conducting electrons and it is very possible that, if we come in contact with a high voltage source, our body could be severely burnt. That is why electricians wear rubber gloves when they work with electricity

Resistance
If you have two conductors of the same size and shape, but made from different materials, the amount of current that will flow through them depends on the resistance of the materials. The lower the resistance value, the greater the current flow will be. Resistance is measured in Ohms. Resistance will always produce heat. A light bulb and a toaster are examples of electrical resistance.

A circuit has the resistance of one ohm when an emf of one volt causes one amp of current flow. A copper wire ten feet long will have twice the resistance as a five-foot piece of the same wire. The longer the path that a current must flow in a conductor, the higher the resistance will be. A “package” of resistance made up into a single unit is called a resistor and is usually made of carbon. Carbon is a conductor with very unique and constant properties.

Drawing of resistor and schematic symbol of resistor

Resistors of the same value in Ohms can be very different in size and shape. The flow of current through a resistance causes the material to become heated. The higher the resistance and the larger the current, the greater the amount of heat that will be generated. Resistors that carry large currents must be physically large so they can dissipate the heat into the air. The rate that a material can dissipate heat is proportional to the area that is exposed to the air. It is similar to the way that a large air vent can heat or cool a room faster than a small vent. If the heat cannot be dissipated the resistors could melt or burn.

An Electric Circuit
An electric circuit is defined by a voltage source or battery, a current path like the wires in your home, and a resistance or load like a light bulb. The following drawing is called a schematic of an electric circuit.

Drawing of simple circuit

A complete circuit must have an unbroken path so current can flow from the battery, through the resistance or load, and back into the battery. If the circuit becomes broken, or open, the current cannot flow.