Charles Wayne. - Electronic Circuits: The Definitive Guide to Circuit Boards, Testing Circuits and Electricity Principles

The principles of electricity are as simple as they are elegant. However, before you begin to delve into these principles, it is important to understand what electricity is in the first place. The simplest way to define electricity would be to say that electricity is the movement of an electric current from one place to another. The movement of free electrons from one place to the other causes this electric current, therefore, the more free electrons a material has the better it will be at conducting electricity.

There are various parameters that need to be considered when you discussing the principles of electricity, the most important of which are Coulombs, Volts, Amperes, Ohms and Watts.

1. Coulomb

The coulomb (C) is the internationally accepted (SI) unit of electrical charge. The Coulomb is named after the famous French physicist Charles-Augustin de Coulomb who developed a law by the same name to explain the electrostatic forces of attraction and repulsion. Its symbol is C, and it is used to measure the amount of charge carried by a constant current along a conductor in one second.

It can be described mathematically as: 1 C = 1 A x 1 S

1 C is roughly 6.242 x 10 or 1.036 x 10 -5 mol Protons, while -1 C is just about 6.242 x 10 electrons.

1. Volts

Named after the famous Italian Physicist Alessandro Volta, the Volt (V) is a unit of measurement used to describe the electromotive force (emf) required to drive a current of one ampere through a conductor with a resistance of one ohm.

To simplify this explanation, imagine you have a hydraulic circuit, with a faucet, a pump, a pipe and a trough. The pump helps to draw water into the pipe when the faucet is turned on, and the water flows through the pipe, out of the faucet and back into the trough where the whole cycle starts again.

The volt in this case would be the amount of pressure that the circuit would need to get the water through it.

The volt can mathematically be represented in a number of ways. Expressing it in SI units (the seven internationally accepted units of measurement) can be done as follows:

V= Potential Energy/Charge = N x m/coulomb =

Kg x m x m/ s x A x s = Kg x m 2/ A x s

1. Ampere

An ampere (A) or an amp is the SI unit for electric current. It is equivalent to 1 coulomb, and is used to describe the flow rate of an electrical charge. The ampere is named after Andr-Marie Ampre, a French physicist and mathematician that was central to the development of classical electromagnetism during the early part of the 19 th century.

It is important to remember that the amp should never be confused with the coulomb. This is because the coulomb is a unit of charge, where as the amp is a unit of current, or the amount of charge moving through the circuit at any given time.

It should come as no surprise then to realize that should there be an increase in the number of charged particles passing through a specific point, then there should also be a rise in the amperes of current.

Amperes can be mathematically expressed as follows:

1A = 1 C/s

1. Ohms

The ohm () is a unit of measurement that is used to describe electrical resistance through any conductive material. It was named after the German physicist and mathematician, Georg Simon Ohm, who was a one of the pioneers in the study of electricity.

He developed a law by the same name (Ohms Law) to describe the relationship between a conductor, the potential difference (voltage) applied to it, and the consequent electric current. The law describes the ohm as an electrical resistance in a circuit transmitting a current of one ampere when subjected to a potential difference of one volt.

Basically, it states that the ohm is the resistance to the passage of electricity through a conductor should the said conductor have an electric current of 1 ampere pass through it, and a potential difference of 1 volt.