10th Class Science Electricity and Circuits Introduction

       Introduction

One of the important sources of energy in modern time is the electricity. Modern life depends on electricity to a very large extent. All the modern development has been made possible due to the electricity. It is used everywhere, in house, in industry, transportation, and in what not?. Now the most important question is 'how is electricity produced?' and 'what is electricity'?

       Electricity

Atom consists of charge particles, such as, proton and electron. Protons are the positive charge particles and electrons are the negative charge particles, present in an atom. Electric current is generated by flow of charges through the conductors. It depends on the amount of charge flowing through the conductor, through a particular area and in a unit time. The rate of the flow of electric charge through the conductor is called the electric current. Conventionally, in an electric circuit the direction of electric current is taken as opposite to the direction of the flow of electrons, which are negative charges. If \[{{q}_{1}},\,\,{{q}_{2}},\,\,{{q}_{3}},\,\,{{q}_{4}}--,{{q}_{n}}\] are the n charges flowing through the conductor in a given time t, then the current flowing through the conductor of given cross sectional area is given by

\[I=\frac{{{q}_{1}}+{{q}_{2}}+{{q}_{3}}+{{q}_{4}}+----+{{q}_{n}}}{t}\]

\[\Rightarrow \,\,I=\frac{Q}{t},\]where Q is the net charges given by,

\[Q={{q}_{1}}+{{q}_{2}}+{{q}_{3}}+{{q}_{4}}+----+{{q}_{n}}\]

I is the current produced

t is the time for which the charge flows

The SI unit of electric charges is coulomb (C), which is equivalent to the charge contained in nearly \[6\times {{10}^{8}}\] electrons. The unit of electric current is ampere which is named after the French scientist Marie Ampere. One ampere current is equivalent to the current produced by flow of one coulomb of charge in one second. We can measure the current with the help of an instrument called Ammeter by connecting it in series in the electric circuit.

If we rub an ebonite rod with woolen cloth, the charge acquired is negative and if we rub glass rod with silk cloth the charge acquired is positive. There are some substances through which electric charge can flow easily and hence are called conductors. But there are some substance through which the charge cannot flow easily, are called semi-conductors. Some substance through which electric current cannot flow at all are called insulators. The metals like copper, Aluminium are good conductor of electricity. Some of the alloy such as nichrom, manganin, and constantan are also the good conductor of electricity.

In fact, human body is also the good conductor of electricity. On the other hand substance like plastics, rubber, glass, ebonite, dry wood, etc do not allow the electric current to flow through it and are the example of insulators. It is actually the presence of free electron, which are loosely bound with the atoms, are responsible for constituting electric current through the conductors. In case of insulators, the electrons are strongly held by the atoms and are not free to move about. Hence electricity is divided into two categories as static electricity and current electricity. In static electricity, the electric charge remains at rest. For example, charge acquired by ebonite rod, glass rod rubbing with woolen cloth and silk cloth etc. are static electricity. The electricity we are using at our home is current electricity. In current electricity, the charge are in continuous motion.