Introduction

 

 what exactly is electricity ??????

At the level of atomic physics, electricity is one of the fundamental forces of nature, arising from an "electric charge" possessed by subatomic particles (notably protons and electrons).
At a practical level, electricity describes the phenomena associated with the bulk behavior of aggregates of enormous numbers of those charged particles in normal matter. Just as the observed mass of ordinary objects arises from the mass of the constituent particles, the observed behavior of electricity in ordinary objects arises from the electric charges of the constituent subatomic particles. In fact, ordinary electrical phenomena arise from incredibly tiny differences between the number of positively charged protons and negatively charged electrons. In ordinary "electrically neutral" matter, the positive and negative charges cancel essentially exactly, so no electrical properties are observed. The imbalance between protons and electrons in matter exhibiting electrical phenomena is exceedingly small—a golf ball with a charge of 10,000 volts has an electron excess or deficit of only 1 part in 10<sup>13


In fact, early researchers in electricity in the 18th and 19th centuries saw this, and referred to the "electrical fluid". They even noticed that this "fluid" could be stored in "Leyden jars", which were glass jars with metal foil on the inside and outside. We now know that the jars were just capacitors with the glass as the dielectric, and that the fact that they were jars was a coincidence. We now rate capacitors in farads; early researchers rated them in quarts.</sup>
The unit of quantity of electric charge is the coulomb, abbreviated "C", and named after Charles-Augustin Coulomb^. 
  It is 6.241 x 10¹⁸ elementary charges. Or equivalently, the elementary charge (charge on a single electron or proton) is 1.602 x 10^-19 coulombs. In the hydraulic analogy, it is analogous to a liter of fluid. But unlike water, electric charge can be either positive (deficit of electrons) or negative (excess of electrons.)

Flow of charge—what we call current—could be thought of as flow of positive charge in one direction, or of negative charge in the other direction. By convention, current flow is always considered to be the flow of positive charge, even though that is contrary to the actual flow of (negative) electrons. Hence the current is considered to flow out of the positive terminal of a battery, through whatever is being powered, and back into the negative terminal, even though electron flow through the wires is in the opposite direction.

The unit of current flow is the ampere, abbreviated "A", which is a flow rate of one coulomb per second. It is named after André-Marie Ampère. In the hydraulic analogy, it is analogous to the amount of flow through a pipe, or over a dam, etc., which might be measured in liters per second with the hydraulic analogy.