E l e c t

r i c

i t y

What is electricity?Electricity (from the New Latin ēlectricus, "amber-like") is

a general term that encompasses a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena, such as lightning and static electricity, but in addition, less familiar concepts, such as the electromagnetic field and electromagnetic induction.

"a fundamental entity of nature consisting of negative and positive kinds."

History of Electricity……. ♥Long before any knowledge of electricity existed people were aware of shocks from electric fish. Ancient Egyptian texts dating from 2750 BC referred to these fish as the "Thunderer of the Nile", and described them as the "protectors" of all other fish. They were again reported millennia later by ancient Greek, Roman and Arabic naturalists and physicians. Several ancient writers, such as Pliny the Elder and Scribonius Largus, attested to the numbing effect of electric shocks delivered by catfish and torpedo rays, and knew that such shocks could travel along conducting objects. Patients suffering from ailments such as gout or headache were directed to touch electric fish in the hope that the powerful jolt might cure them. Possibly the earliest and nearest approach to the discovery of the identity of lightning, and electricity from any other source, is to be attributed to the Arabs, who before the 15th century had the Arabic word for lightning (raad) applied to the electric ray. That certain objects such as rods of amber could be rubbed with cat's fur and attract light objects like feathers was known to ancient cultures around the Mediterranean. Thales of Miletos made a series of observations on static electricity around 600 BC, from which he believed that friction rendered amber magnetic, in contrast to minerals such as magnetite, which needed no rubbing. Thales was incorrect in believing the attraction was due to a magnetic effect, but later science would prove a link between magnetism and electricity. According to a controversial theory, the Parthians may have had knowledge of electroplating, based on the 1936 discovery of the Baghdad Battery, which resembles a galvanic cell, though it is uncertain whether the artifact was electrical in nature.

Benjamin Franklin conducted extensive research on electricity in the 18th centuryElectricity would remain little more than an intellectual curiosity for millennia until 1600, when the English physician William Gilbert made a careful study of electricity and magnetism, distinguishing the lodestone effect from static electricity produced by rubbing amber. He coined the New Latin word electricus ("of amber" or "like amber", from ήλεκτρον [elektron], the Greek word for "amber") to refer to the property of attracting small objects after being rubbed. This association gave rise to the English words "electric" and "electricity", which made their first appearance in print in Thomas Browne's Pseudodoxia Epidemica of 1646. Further work was conducted by Otto von Guericke, Robert Boyle, Stephen Gray and C. F. du Fay. In the 18th century, Benjamin Franklin conducted extensive research in electricity, selling his possessions to fund his work. In June 1752 he is reputed to have attached a metal key to the bottom of a dampened kite string and flown the kite in a storm-threatened sky. A succession of sparks jumping from the key to the back of the hand showed that lightning was indeed electrical in nature.

Michael Faraday formed the foundation of electric motor technologyIn 1791, Luigi Galvani published his discovery of bioelectricity, demonstrating that electricity was the medium by which nerve cells passed signals to the muscles. Alessandro Volta's battery, or voltaic pile, of 1800, made from alternating layers of zinc and copper, provided scientists with a more reliable source of electrical energy than the electrostatic machines previously used. The recognition of electromagnetism, the unity of electric and magnetic phenomena, is due to Hans Christian Ørsted and André-Marie Ampère in 1819-1820; Michael Faraday invented the electric motor in 1821, and Georg Ohm mathematically analysed the electrical circuit in 1827. While it had been the early 19th century that had seen rapid progress in electrical science, the late 19th century would see the greatest progress in electrical engineering. Through such people as Nikola Tesla, Thomas Edison, Ottó Bláthy, Sir Charles Parsons, George Westinghouse, Ernst Werner von Siemens, Alexander Graham Bell and Lord Kelvin, electricity was turned from a scientific curiosity into an essential tool for modern life, becoming a driving force for the Second Industrial Revolution.

Ohm's Law defines the relationships between (P) power, (E) voltage, (I) current, and (R) resistance. One ohm is the resistance value through which one volt will maintain a current of one ampere.

( I ) Current is what flows on a wire or conductor like water flowing down a river. Current flows from negative to positive on the surface of a conductor. Current is measured in (A) amperes or amps.

( E ) Voltage is the difference in electrical potential between two points in a circuit. It's the push or pressure behind current flow through a circuit, and is measured in (V) volts.

( R ) Resistance determines how much current will flow through a component. Resistors are used to control voltage and current levels. A very high resistance allows a small amount of current to flow. A very low resistance allows a large amount of current to flow. Resistance is measured in ohms.

( P ) Power is the amount of current times the voltage level at a given point measured in wattage or watts.

· Electric charge – a property of some subatomic particles, which determines their electromagnetic interactions. Electrically charged matter is influenced by, and produces, electromagnetic fields.

· Electric field – an influence produced by an electric charge on other charges in its vicinity.

· Electric potential – the capacity of an electric field to do work on an electric charge, typically measured in volts.

Electric current – a movement or flow of electrically charged particles, typically measured in amperes.

- is the movement of the charged particles in a specific direction. The charge particle may be an electron, a positive ion of a negative ion, and they are referred to as current carries.

Current – is the measure of how much charge is passed through a given point in a conductor per given amount of time.

- the symbol for current is I.

Direct current (DC) is the unidirectional flow of electric charge. Direct current is produced by such sources as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. Direct current may flow in a conductor such as a wire, but can also be through semiconductors, insulators, or even through a vacuum as in electron or ion beams.

Alternating current (AC, also ac) the movement (or flow) of electric charge periodically reverses direction. An electric charge would for instance move forward, then backward, then forward, then backward, over and over again.

The electrical resistance of an object is a measure of its opposition to the passage of a steady electric current. An

object of uniform cross section will have a resistance proportional to its length and inversely proportional to its

cross-sectional area, and proportional to the resistivity of the material.

Discovered by Georg Ohm in the late 1820s,[1] electrical resistance shares some conceptual parallels with the mechanical notion of friction. The SI unit of electrical

resistance is the ohm, symbol Ω. Resistance's reciprocal quantity is electrical conductance measured in siemens,

symbol S.

Problems

for

Electricity

EXAMPLE

Problem 1: An appliance draws 10 amperes in a 110 volt circuit. What is the

resistance of the appliance?

Given: 10 amps110 volts

Find the resistance The formula is Volts = amps X ohms

Therefore, volts/amps = ohms, because of the substitution to get the formula for the ohms.

Solution:volts/amps = ohms

110 volts/10 amps = 11 ohmsThe resistance is 11 ohms.

Problem 2:A 10 ohm resistor is connected to a 100 volt source. What current does it

draw?

Given:10 ohm 110 volt

Find the current. The formula is amps = volts/ohms

Solution:amps = volts/ohms

100 volts/10 ohms = 10 ampsDividing the 100 volts over 10 ohms is equal to 10 amps. Therefore

the current is 10 amps.

Problem 3:A 10 ohm resistor draws 9 amps. What is the voltage across the resistor?

Given:10 ohm9 amps

Find the voltage The formula is volts = amps x ohms.

Solution:volts = amps x ohms

9 amps x 10 ohms = 90 volts.Multiplying the 9 amps and 10 amps will have the product of 90 volts.

Therefore the voltage is 90 volts.

The End….

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