ELECTRICITY:



Electricity:



Electricity has changed the daily life of everybody on the planet. Electricity is very essential part of our daily life. Life without electricity is unimaginable, almost everything depends on electricity. Electricity one of most precious gift that science has given to mankind. Lets know the famous personalities who gave most valuable gift to mankind.





Around 600BCE, Thales of Miletus made series of observations on static electricity, they knew certain objects, such as rods of amber could be rubbed with cats fur to attract light objects like feathers. They believed that attraction was due to magnetic effect, but later science proved link between magnetism and electricity.



Around 1600, the English scientist William Gilbert wrote De Magnete, in which he made careful study of electricity and magnetism, distinguishing Iodestone effect from static electricity produced by rubbing amber. He named new Latin word electricus (“of amber” or “like amber”). Later on, the Greek word elektron , referred to the property of attracting small objects after being rubbed. The association gave rise to the English words “Electric” or “Electricity”.



Up until that time, scientists had mainly known about and experimented with static electricity. Benjamin Franklin took things a big step ahead. He came up with the idea that electricity had positive and negative elements and that electricity flowed between these elements. He also believed that lightning was a form of this flowing electricity.



In 1752, Franklin conducted his famous kite experiment. In order to show that lightning was electricity, he flew a kite during a thunderstorm. He tied a metal key to the kite string to conduct the electricity. Just as he thought, electricity from the storm clouds transferred to the kite and electricity flowed down the string and gave him a shock. He's lucky that he didn't get hurt, but he didn't mind the shock since it proved his idea.



In 18th century, the extensive research in electricity made by Benjamin Franklin by selling his possession to fund for the work. He also explained the behaviour of Leyden jar as device for storing large amounts of electrical charges in terms of electricity consisting of both positive and negative charges.



Building upon Franklin's work, many other scientists studied electricity and began to understand more about how it works. For example, in 1879, Thomas Edison invented the electric light bulb and our world has been brighter ever since!



But was Benjamin Franklin really the first person to discover electricity? Maybe not! At the turn of the 17th century, English scientist William Gilbert established the science underlying the study of electricity and magnetism. Inspired by Gilbert's work, another Englishman, Sir Thomas Browne, made further investigations and wrote books about his findings. Gilbert and Browne are credited with being the first scientists to use the term "electricity."



Alessandros Volta’s battery, or voltaic pile, of 1800 made from alternating layer of Zinc and copper provided reliable source of electricity than the electrostatic machines previously used.



In 1821, Michael Faraday invented the electric motor and George Ohm mathematically analysed the electrical circuit in 1827. Electricity and magnetism were definitely linked by James clerk Maxwell.



In 1887, Heinrich Hertz discovered that electrodes illuminated with ultraviolet light create electrical sparks more easily.



In 1905, Albert Einstein published a paper that explained experimental data from photo electric effect as being the result of light energy being carried in discrete quantized packets, energising electrons. This discovery led to the quantum revolution. The photoelectric effect employed in photocells which is normally found in solar panels.




Basics of Electricity:

Electricity is defined as the flow of charged particles called electrons through a conductive medium.



The movement of electric charge is known as electric current, the intensity of which usually measured in amperes. Current can consist of moving charged particles called electrons.



A positive current is defined as having the same direction of flow as any positive charge it contains, or flow from the positive part to negative part.



The motion of negatively charged electrons around an electric circuit, one of most familiar form of current, is thus deemed positive in the opposite direction to that of the electrons.



However depending on the conditions, an electric current can consist of a flow of charged particles in either direction, or even in both directions at once.



The electric current can flow through electrical conductors, but will not flow through an electrical insulator.



The process by which electric current passes through a material called electrical conduction.



The current is often described as either Direct Current(DC) or Alternating Current(AC) . These terms indicated how current varies in time.



DC is produced by battery and required by most electronic components of equipment. DC is having unidirectional flow of current from positive part of circuit to the negative . If, the flow is carried by electrons, they will be(current) travelling in opposite direction.



AC is any current that reverses the direction repeatedly. AC pulses back and forth within a conductor



without the charge moving any distance over the time. The time averaged value of AC is zero.



a.Electric Field:
  1. This is introduced by Michael Faraday.

  2. Electric field is created by charged body in a space that surrounds it and results in force exerted on any other charges placed within the body.

  3. Electric field either result in attraction or repulsion.

  4. Electric fields varies in space and its strength at any one point is defined as force (per unit charge), that would be felt by stationary, negligible charge if placed at that point.

  5. “Test charge” must be small to prevent its own electric field disturbing the main field and must also be stationary to prevent effect of magnetic fields.

  6. Electric field defined in terms of force-force is a vector, having both magnitude and direction.

  7. The study of electric fields created by stationary charges is called electro statistics.



b.Electric Potential:
  1. The electric potential at any point is defined as energy required to bring a unit charge from an infinite distance to that point.

  2. It is usually measured in volts.

  3. 1Volt of potential is required to bring one coulomb of charge from infinity.(for doing 1joule of work)

  4. Electric potential difference means energy required to move unit of charge between two specified points.

  5. Electric field is conservative, means the path taken by test charge is irrelevant.

  6. For practical purposes –common reference point is referred which could be at infinity. Earth itself assumed to be same potential everywhere. The reference point naturally named as earth or ground.

  7. Earth is assumed as infinite source of equal amounts of positive and negative charge, and is therefore electrically uncharged-and unchargeable.

  8. Electric potential is scalar quantity, it has only magnitude not direction.



c.Electromagnets:
  1. In 1821, Orsted’s discovered that magnetic field existed around all sides of a wire carrying an electric current.

  2. Later Ampere discovered that two parallel current carrying wires exerted a force upon each other. Two wires conducting current in the same direction are attracted to each other, while wires containing currents in opposite directions are forced apart. The interaction is mediated by the magnetic field each current produces.

  3. The electric motor exploits an important effect of electromagnetism. A current through a magnetic field experiences a force at right angles to both the field and current.

  4. Experimentation by Faraday in 1831 revealed that wire moving perpendicular to a magnetic field developed potential difference between its ends.

  5. Further analysis if this process, enabled him to state the principle , known as Faraday’s Law of induction, that the potential difference induced in a closed circuit is proportional to the rate of change of magnetic flux through the loop.

  6. Using this discovery, enabled him to invent first electrical generator in 1831, in which he converted mechanical energy of rotating copper disc to electrical energy.



d.Electrochemistry:
  1. The ability of chemical reactions to produce electricity has increased the ways of using it in our daily lives.

  2. After invention of voltaic pile, electrochemical cells used in many different types of batteries, electroplating and electrolysis cells.

  3. Aluminium produced in vast quantities, many portable devices powered using rechargeable cells.



e.Electric Circuit:
  1. An electrical circuit is interconnection of electrical components such that electric charge is made to flow along a closed path(a circuit), usually to perform some useful task. Ohm’s law is basic law of circuit theory.

  2. The components such as resistors, capacitors, switches, transformers and electronics.

  3. Resistor: -This is passive circuit element. It resists the current through it, dissipating its energy as heat. The unit of resistance is Ohm,named after George Ohm.

  4. For example: resistance is due to collision between electrons and ions. 1ohm is resistance that will produce a potential difference of 1V in response to the current of 1A.



f.Capacitor:
  1. The Capacitor is development of Leyden jar and is a device that can store charge, thereby stores electrical energy in the resulting field.

  2. It consists of two conducting plates separated by thin insulating dielectric layer. The unit of resistance is the farad, named after Michael Faraday and given symbol F.

  3. For example: 1F is the capacitance that develops potential difference of 1V when it stores a charge of 1Coulomb.



g.Inductor:
  1. Inductor is conductor usually coil of wire that stores energy in a magnetic field in response to current through it.

  2. When current changes , the magnetic field also changes, inducing a voltage between the ends of conductor.

  3. The induced voltage is proportional to the time rate of change of current.

  4. The constant of proportionality is termed as inductance.

  5. The unit of inductance is henry, named after Joseph Henry.

  6. For Example : One Henry is the inductance that will induce potential difference of 1V if current through it changes at a rate of 1ampere per second.



h.Electric Power:
  • Electric Power is the rate at which electrical energy is transferred by an electrical circuit. The SI unit of power is watt, one joule per second.

  • The electric power in watts produced by an electric current I consisting of a charge of Q coulombs every t seconds passing through an electric potential(voltage) difference of V is,


  • P=work done per unit time=QV/t=IV

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