There are two types of electricity. One is static electricity and the other is current electricity. To know about electricity accurately, the following terms and there explanation should be understood.
- Charge : Amount of electricity is called charge. The name of the unit of charge in SI system is coulomb. What is coulomb? The amount of charge which when is sent through silver nitrate solution 0.001118 gram silver is deposited on the cathode plate, is called 1 coulomb.
The existence of electricity means the existence of electron. One electron possesses 1.6 x 10^-19 coulomb charge. So, static electricity is an accumulation of electrons in a place or the absence of electrons in a place.
The absence of electrons in a place means the existence of positive static electricity.
The accumulation of electrons in a place means the existence of negative static electricity.
The flowing of electrons from one place to another through a electric conductor is called the current electricity.
- Electric potential : The work done to bring unit positive charge from infinity to a place is called the potential of that point.
If one Jule work is done to bring one coulomb positive charge to a place from infinity then the potential of that point is called one Volt.
Volt is the name of unit of potential in SI system.
So, if 'W' amount of work is done to bring 'Q' coulomb positive charge from infinity to a place with potential 'V' volt then it can be easily written that W=VQ i.e. work=potential x charge i.e. Jule=Volt x Coulomb.
- Electric current : When there is a current of electrons in a conductor, it is called that electric current is flowing through the conductor. The place where is scant of electrons is called positive pole or anode. The place where is abundance of electron is called negative pole or cathode.
When electrons are flowing from negative place to positive place through a conductor, conventionally, it is called that electric current is flowing from positive place to negative place.
The unit of electric current in SI is Ampere. When 1 coulomb charge is flowing in 1 second then it is called that 1 ampere electric current is flowing.
So, if 'Q' amount of charge is flowing in 't' seconds and 'I' amount of electric current is flowing through a conductor then it can be written that I=Q/t or Ampere=Coulomb/ second.
- Electromotive force : When two places with different potential are not connected with a conductor, a force is in work to send electrons from one place to another. This force is called electromotive force.
The place with lower number of electrons coventionally is called higher potential place and the place with higher electrons conventionally is called lower potential place.
- Potential difference : When two places with different potential is connected with a conductor then some electrons flow from lower potential place to higher potential place. At once electromotive force decreases by a little amount. This lessened electromotive force between those places is called potential difference.
Potential difference comes in a closed circuit where as electromotive force comes in open circuit. emf is the cause where as potential difference is its effect. Where electric energy is changed into heat etc other energies, potential difference is created where as when other energies are transferred into electric energy, emf is created. The unit of the both of emf and potential difference is the same in SI unit system that unit is volt.
- Circuit : The path through which electricity or electron is flowing is called the circuit.
There are two types of circuit. One is open circuit and the other is closed circuit.
The electric circuit which has two open ends is called open circuit and the circuit which has no open end is called the closed circuit.
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