Without electricity, our entire modern world will be pushed back to the stone age. The question is what is or what causes this electricity. We can perceive electricity as some form of energy that makes all the electronic devices work, but really to understand the electricity or electric current, we must understand the structure of atoms and the behaviour of subatomic particles; which is nothing but the electrons.
Electric Current
This is the basic idea, when an atom of a particular element, say silver or copper, is ready to lose electrons; they become conductors because of the loosely bound outer valence electrons. This means that electrons can easily flow through metals. When a potential difference is set (using a battery), the electrons of the conductor drift towards the positive terminal. This drifting of electrons or flow of electrons is called current. In other words flow of charges is called current.
The term current we normally use is called "conventional current", in which we say the charge has flowed from the positive side to the negative side but actually it is the electrons that have flowed in the opposite direction. This conventional current is denoted by the letter or symbol, I and is expressed in the unit Ampere or A.
Current is calculated using the well-known equation
I = Q/T
Where I is current in Ampere, Q is charge in coulomb and T is the time taken for the charges to pass through a given cross-sectional area of a conductor.
1 coulomb is nothing but the total charge of 6,250,000,000,000,000,000 electrons. (1 electron has a charge of 1.60217663 × 10 power -19 coulombs)
Hence, if 6.25 x 10^18 electrons pass through a given area for a time period of one second, we call that 1 Ampere. Similarly, 12.5 x 10^18 (2 times 6.25 x 10^18) electrons pass in one second then it's 2 Ampere.
Potential Difference
Now you may ask what is potential difference? Just like anything else electrons too need a force to push them around in a given circuit, without this force electrons won't flow. This force is made possible by creating a potential difference.
First, the potential is nothing but the energy electrons have at a given location in a circuit, this potential energy is gained because electrons are at a certain distance from positive charges also they are separated from each other. More the magnitude or size of the charges greater this potential will be. This potential difference can be created by a battery.
At this point, where electrons are longing to join positive charges; we create a pathway using conductors such as copper or silver. And hence the electrons flow from the negative side because the negative terminal of the battery repels electrons (like charges repel) and to the positive terminal of the battery.
The nature of charges to repel or attract is the key to this force. This force that causes the charge to move is called the potential difference or voltage. In simple terms, we pull the electrons apart from the positive charges, this gives electrons potential energy to go back to the positive charges. We separate electrons and positive charges and we want these electrons to reach the positive side in the way or path we want; as the electrons flow in the path we wanted, we use the kinetic energy of the flow for our energy needs such as light, sound, heat and more. The energy difference causes the electrons to flow around the circuit such as marbles running down the slope.
The unit of voltage or Potential difference is volt and is represented by the letter v.
V = W/A OR V = J/C
When an electric current of one ampere produces a power of 1 watt, then 1 volt of potential is present. Also if 1 coulomb of charge produces 1 joule of energy then again you got 1 volt of potential difference.
The equation from ohm's laws gives a relationship between current, voltage and Resistance.
V = IR
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