Wikipedia's facts - electric charge
Electric charge is the physical property of matter that causes it to experience a force when placed in an electromagnetic field. There are two types of electric charges: positive and negative. Like charges repel and unlike attract. An object (one not made of antimatter) is negatively charged if it has an excess of electrons, and is otherwise positively charged or uncharged. The SI derived unit of electric charge is the coulomb (C). In electrical engineering, it is also common to use the ampere-hour (Ah), and, in chemistry, it is common to use the elementary charge (e) as a unit. The symbol Q often denotes charge. Early knowledge of how charged substances interact is now called classical electrodynamics, and is still accurate for problems that don't require consideration of quantum effects.
The electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. Electrically charged matter is influenced by, and produces, electromagnetic fields. The interaction between a moving charge and an electromagnetic field is the source of the electromagnetic force, which is one of the four fundamental forces (See also: magnetic field).
The danger when working with electricity
Occupation electrician is very often seen as a profession in which extremely common ones are physical injury. This is related primarily to the fact that when working with electricity, even the smallest mistake can cause severe short circuit, which would be harmful to human health. Usually created a power failure is unexpected and electrician seeking a solution to the problem moves groping. Therefore, for such a mistake it is very easy and you can tell that no theoretical knowledge is not able to prepare the employee to perfect the profession, because of some random events can not be predicted.
Different levels of electricians - Wikipedia
Electricians are trained to one of three levels: Apprentice, Journeyman, and Master Electrician. Apprentices in the US and Canada are working to learn the electrical trade. They generally take several hundred hours of classroom instruction and are contracted to follow apprenticeship standards for a period of between three and six years, during which time they are paid as a percentage of the Journeyman's pay. Journeymen are electricians who have completed their Apprenticeship and who have been found by the local, State, or National licensing body to be competent in the electrical trade. Master Electricians have performed well in the trade for a period of time, often seven to ten years, and have passed an exam to demonstrate superior knowledge of the National Electrical Code, or NEC.