ELECTRICITY  :
It is the branch of physics which deals with the study of interaction of one charge to the another charge. It can be divided into two part :

(i) Static Electricity          (ii) Current Electricity
(a)     Static Electricity : The branch of physics which deals with the study of the electric charges at rest and their effects is known as electrostatic or static electricity.
(b)     Current Electricity : The branch of physics which deals with the study of the electric charges in motion and their effects is known as current electricity.

Use of Electricity : We use electricity for many purposes to make our tasks easier. For example, we use electricity to operate pumps that lift water from wells or from ground level to the roof top tank. Electricity makes it possible to light our homes, roads, offices, markets and factories even after sunset. This helps us to continue working at night.

Source of Electricity: Mainly two types of Sources of Electricity

1.    Power Station : It is  a Main Source of Electricity. It produces and supply huge amount of Electricity. All the high voltage equipment get the supply from power station.

2.    Electric Cells (Batteries) :It gives little amount of Electricity. It is portable and safe.

SYMBOLS OF ELECTRIC COMPONENTS :
The following are the symbols for some electric circuit components.

ELECTRIC CHARGE :
From the study of atomic structure we know that an atom consists of a central part called nucleus and around the nucleus (called extra-nucleus) there are a number of electrons revolving in different paths or orbits. The nucleus consist of protons and neutrons. A proton is a positively charged particle while a neutron has no charge. Therefore, the nucleus of an atom bears a positive charge. An electron is a negatively charged particle having magnitude of negative charge equal to the magnitude of positive charge on a proton. Normally, the number of electrons is equal to the number of protons in an atom. Therefore, an atom is neutral as a whole, the negative charge on electrons cancelling the positive charge on protons. This leads to the conclusion that under ordinary conditions, a body is neutral, i.e. it exhibits no charge. When a body has deficiency or excess of electrons from the normal, it is said to be charged or electrified.