1. Conductor – is a material which contains movable electric charges. In metallic conductors such as copper or aluminum, the movable charged particles are electrons (see electrical conduction). Positive charges may also be mobile, such as the cationic electrolyte(s) of a battery, or the mobile protons of the proton conductor of a fuel cell. In general use, the term “conductor” is interchangeable with “wire. 2. Insulators – are non-conducting materials with few mobile charges and which support only insignificant electric currents. 3. Atom – is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons.
The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons (except in the case of hydrogen-1, which is the only stable nuclide with no neutrons). 4. Electric charge – is a physical property of matter that causes it to experience a force when near other electrically charged matter. Electric charge comes in two types, called positive and negative. Two positively charged substances, or objects, experience a mutual repulsive force, as do two negatively charged objects.
Positively charged objects and negatively charged objects experience an attractive force. 5. A simple circuit contains the minimum things needed to have a functioning electric circuit. A simple circuit requires three (3) things:
* A source of electrical potential difference or voltage. (typically a battery or electrical outlet) * A conductive path which would allow for the movement of charges. (typically made of wire) * An electrical resistance (resistor) which is loosely defined as any object that uses electricity to do work. (a light bulb, electric motor, heating element, speaker, etc.) 6. Electrical circuit – is a path which electrons from a voltage or current source follow. Electric current flows in a closed path called an electric circuit. The point where those electrons enter an electrical circuit is called the “source” of electrons. The point where the electrons leave an electrical circuit is called the “return” or “earth ground”.
The exit point is called the “return” because electrons always end up at the source when they complete the path of an electrical circuit. The part of an electrical circuit that is between the electrons’ starting point and the point where they return to the source is called an electrical circuit’s “load”. 7. Ohm’s law – says that in an electrical circuit, the current passing through a resistor between two points, is related to the voltage difference between the two points, and inversely related to the electrical resistance between the two points. This relation is shown in the following formula:
where I is the current in amperes, V is the potential difference in volts, and R is a constant, measured in ohms, called the resistance.
It also says that current is directly proportional to voltage loss though a resistor. That is if current doubles then so does voltage. To make a current flow through a resistance there must be a voltage across that resistance. Ohm’s Law shows the relationship between the voltage (V), current (I) and resistance (R). It can be written in three ways: