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Fundamentals of Electricity in Nature:Understand the Role of electron and it’s flow (Current) behind it

Introduction

Everybody is familiar with the functions that electricity can perform. It can be used for lighting, heating, traction and countless other purposes.The question always arises, “What is electricity”? Several theories about electricity were developed through experiments and by observation of its behaviour.Electricity is a fundamental force of nature that has been harnessed and explored by humans for centuries. It powers our homes, fuels our technology, and underpins the functioning of our bodies. Understanding the nature of electricity is crucial for a wide range of applications, from powering our homes to revolutionizing modern technology. In this blog, we'll delve into the captivating world of electricity, its nature, and its many manifestations.
A glowing lightbulb hovers against a gradient background of warm orange and purple tones. Below, the text reads "Nature of Electricity."

Nature of Electricity

We know that matter is electrical in nature i.e. it contains particles of electricity viz. protons and electrons. The positive charge on a proton is equal to the negative charge on an electron. Whether a given body exhibits electricity (i.e. charge) or not depends upon the relative number of these particles of electricity.

  1. If the number of protons is equal to the number of electrons in a body, the resultant charge is zero and the body will be electrically neutral. Thus, the paper of this book is electrically neutral (i.e.paper exhibits no charge) because it has the same number of protons and electrons.
  2. If from a neutral body, some electrons are removed, there occurs a deficit of electrons in the body. Consequently, the body attains a positive charge.
  3. If a neutral body is supplied with electrons, there occurs an excess of electrons. Consequently, the body attains a negative charge.

Unit of Charge

The charge on an electron is so small that it is not convenient to select it as the unit of charge.In practice,coulomb is used as the unit of charge i.e.SI unit of charge is coulomb abbreviated as C.One coulomb of charge is equal to the charge on `6.25times10^{16}` electrons, i.e.

1 coulomb = Charge on `6.25times10^{16}` electrons

Thus when we say that a body has a positive charge of one coulomb (i.e. +1 C), it means that the body has a deficit of `6.25times10^{16}` electrons from normal due share. The charge on one electron is given by;

Charge on electron =`-frac1{6.25times10^{16}}`

Mechanism of Current Conduction in Metals

Every metal has a large number of free electrons which wander randomly within the body of the conductor somewhat like the molecules in a gas.The average speed of free electrons is sufficiently high (`10^5` `ms^{-1}`) at room temperature. During random motion, the free electrons collide with positive ions (positive atoms of metal) again and again and after each collision, their direction of motion changes. When we consider all the free electrons, their random motions average to zero. In other words, there is no net flow of charge (electrons) in any particular direction. Consequently, no current is established in the
conductor.

Diagram of an electric circuit featuring random zigzag paths within a rectangle labeled "Copper wire," indicating electron movement, with a battery symbol below.
 

When potential difference is applied across the ends of a conductor (say copper wire) as shown in above Figure electric field is applied at every point of the copper wire.The electric field exerts force on the free electrons which start accelerating towards the positive terminal (i.e., opposite to the direction of the field). As the free electrons move, they collide again and again with positive ions of the metal. Each collision destroys the extra velocity gained by the free electrons.The average time that an electron spends between two collisions is called the relaxation time (t). Its value is of the order of `10^{-14}` second.

Although the free electrons are continuously accelerated by the electric field, collisions prevent their velocity from becoming large.The result is that electric field provides a small constant velocity towards positive terminal which is superimposed on the random motion of the electrons.This constant velocity is called the drift velocity.

The average velocity with which free electrons get drifted in a metallic conductor under the influence of electric field is called drift velocity.The drift velocity of free electrons is of the order of `10^{-5}` `ms^{-1}`.

Thus when a metallic conductor is subjected to electric field (or potential difference),free electrons move towards the positive terminal of the source with drift velocity.Small though it is, the drift velocity is entirely responsible for electric current in the metal.

Relation Between Current and Drift Velocity

Consider a portion of a copper wire through which current I is flowing as shown in Figure. Clearly, copper wire is under the influence of electric field.
Diagram of a copper wire shows electrons moving left with drift velocity, \(v_d\). Electric field \(E\) points right. Area \(A\) highlighted.
Let A = area of X-section of the wire
      n = electron density, i.e., number of free
electrons per unit volume
      e = charge on each electron
      `V_d` = drift velocity of free electrons

In one second, all those free electrons within a distance `V_d` to the right of cross-section at P (i.e., in a volume `AV_d`) will flow through the cross-section at P as shown in Figure.This volume contains n `AV_d` electrons and,hence, a charge (`nAV_d`)e.Therefore, a charge of ne`AV_d` per second passes the cross-section at P.

∴I=ne`AV_d`

Since A, n and e are constant, I`V_d`. Hence,current flowing through a conductor is directly proportional to the drift velocity of free electrons.

  1. The drift velocity of free electrons is very small. Since the number of free electrons in a metallic conductor is very large,even small drift velocity of free electrons gives rise to sufficient current.
  2. The current density J is defined as current per unit area and is given by ;
Current density, J = `frac IA` = ne`frac{AV_d}A`
The SI unit of current density is `frac{amperes}{m^2}`.

Electric Current

Electric current refers to the directed flow of free electrons (or electric charge). The concept becomes clearer with the help of the figure below. A copper strip contains a large number of free electrons. When a voltage (or electric pressure) is applied, the free electrons—because of their negative charge—begin to move toward the positive terminal through the circuit. This movement of electrons forms what we call electric current.
 
Diagram of current in a copper strip. Arrows show free electron flow to the left and conventional current to the right in a circuit.
The reader may note the following points :
  1. Current is flow of electrons and electrons are the constituents of matter. Therefore, electric current is matter (i.e. free electrons) in motion.
  2. Electrons actually flow from the negative terminal to the positive terminal through the external circuit of a cell. Before scientists developed the electron theory, people assumed that current flowed from the positive terminal to the negative terminal. This assumption became a well-established convention, and engineers and physicists still use it today. We now refer to this assumed direction as the conventional current.

Unit of Current:

The strength of electric current I is the rate of flow of electrons i.e. charge flowing per second.

Current, I= `frac QT`

The charge Q is measured in coulombs and time t in seconds. Therefore, the unit of electric current will be coulombs/sec or ampere.If Q = 1 coulomb, t = 1 sec,then I = 1/1 = 1 ampere.

One ampere of current flows through a wire when one coulomb of charge passes a cross-section in one second. So, if 5 amperes of current flow through a wire, 5 coulombs of charge pass through any cross-section every second.

Electric Current is a Scalar Quantity

  • Electric current, I= `frac QT`

As both charge and time are scalars, electric current is a scalar quantity.

Types of Electric Current

The electric current may be classified into three main classes:
1.Steady current: When the current’s magnitude stays constant over time, we call it a steady current. Figure 1 shows the graph of steady current versus time. The current maintains the same value as time progresses. A battery typically provides a steady current (d.c.).
Graph showing constant current (I) over time (t). A horizontal line at I with time starting from zero; axis arrows indicate direction of increase.Figure 1 Graph depicting current (I) versus time (t). The curve begins at the origin, rising sharply initially, then leveling off, indicating an exponential growth.Figure 2An alternating current waveform graph with one cycle. It starts at zero, peaks at I, crosses zero at T/2, dips, then returns to zero at time T.
  Figure 3

                                                               

 2.Varying current:When the current’s magnitude changes over time, we call it a varying current. Figure 2 shows the graph of varying current versus time. The current clearly changes its value as time progresses.
 
3.Alternating current: An alternating current continuously changes its magnitude over time and periodically reverses direction. For technical and economic reasons, engineers generate alternating currents in the form of sine or cosine waveforms, as shown in Figure 3. The term 'alternating' refers to how the current flows in one direction from 0 to T/2 seconds (where T is the wave’s time period) and then in the opposite direction from T/2 to T seconds. An a.c. generator produces this type of current with a sine (or cosine) waveform.

The Building Blocks: Electrons and Charges

Electricity arises from the behavior of subatomic particles, especially electrons. Electric charge forms the foundation of all electrical phenomena. Electrons orbit the nucleus of an atom and carry a negative charge, while protons, located in the nucleus, carry a positive charge. Like charges repel, and opposite charges attract.

Static Electricity

Static electricity is one of the most familiar types of electrical phenomena. It occurs when objects become charged due to the transfer of electrons. When objects with different electrical charges touch or rub together, electrons transfer from one to the other, causing a buildup of charge.

The discharge of static electricity produces remarkable effects, such as lightning, where built-up atmospheric charge releases as a bolt of electrical energy. On a smaller scale, static electricity causes hair to stand on end while combing or makes a charged balloon attract small pieces of paper.

Conclusion

Electricity is a powerful and essential force that shapes our world—from the atoms and molecules that form matter to the technologies that drive our daily lives. By learning how electricity works and behaves, we unlock its incredible potential, fuel innovations, and enhance modern conveniences. Whether you flip a light switch, charge your smartphone, or admire a thunderstorm, electricity surrounds us—waiting for us to explore and harness it to advance humanity.
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