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ELECTRICITY

WHAT is Electricity? It is difficult to answer this question as it is such an energy, which is not visible. But its impact can clearly be realized in the Physical affects such as Heat, Light, Motion, Magnet etc.

First of all Greece scientist Thels Amber discovered that when a glass rod is rubbed by a piece of Silk, develops such an energy that it starts attracting small paper pieces. The same effect was found in some other things too. For example, when dry hairs were combed, and the used comb was brought near paper bits, they were attracted towards it. The developed power was named ‘Electric Charge’ and the attraction of paper bits towards the comb or the glass rod, was taken up as the resultant of two dissimilar properties. To understand this, the example of two poles of the magnet (South pole and North pole) can be taken up for consideration. As two like poles of a magnet repel each other and dissimilar poles attract each other, in the same manner two similar poles repel and two dissimilar poles attract each other. The polarity developed in the paper bits was the opposite polarity than that of the glass rod rubbed by silk rag, and as the dissimilar polarities attract each other, so the paper bits were attracted by the glass rod or the comb. These two different polarities were named by the scientists as the positive and the negative charge. A negative property found in this kind of electricity was that it stayed there only where it was produced. So it was called ‘Static Electricity’. Now, because of its such property, it could not be put to any use. Whatsoever effects we find produced because of electricity, are the effects of traveling electricity. This traveling electricity is named the Current Electricity.

According to the Scientist J. Thompson electricity is nothing but the flow of electrons. The flow cannot be watched by the naked eyes but their effect can only be felt. So, according to this phenomena, ‘The current flows in conductor wire, when the electrons travel from its one end to the other’. This is also considered as the modern definition of electricity.

What is Electron?

To understand electrons, it is better first to understand the Molecules and the Atom.

Molecule:

Molecule is the smallest particle of any substance, which contains all the properties of that substance and has its independent existence.

Atom:

When molecule was discovered, it was considered as the smallest particle of a substance. But now the molecule has been divided. These divided particles are called ‘ATOMS’. They have dissimilar properties to that substance and has no independent existence.

Structure of Atom:

The structure of an atom is much complicated. In its center, is its Neucleus, and the Neucleus has protons and electrons in it. The Protons have the positive charge but the Neutrons have no charge. The number of Neutorns and Protons in the Neucleus is always the same. These particles are always moving in a circular motion round the Neucleus as the planate rotated round the sun. These moving particles are called ‘Electrons’, and the way the electrons remain stretched towards the Neucleus, because of certain force. This force is called the Centrifugal Force. The Electrons have the Negative Charge.

The Atoms of different substances have dissimilar structure. Apart from this, the number of electons rotating round the Neucleus is also different circles, which are called ‘Orbits’. In a neutral atom, the number of electron and protons remain the same.

To recognize different orbits, different names are given. First orbit is called ‘K’, second ‘L’, third ‘M’ & fourth ‘N’. The maximum number of electrons in an orbit can be as follows:

Not more than 2 in ‘K’

Not more than 8 in ‘L’

Not more than 18 in ‘M’

Not more than 32 in ‘N’

Electrons Theory:

On the bases mentioned above, the orbits are said to be complete. As and as the distance of the orbits from their Neucleus gets increased, the Centrifugal force goes on decreasing. In this way the Centrifugal Force on the last orbit is minimum. Now these electrons can very easily be parted. And also if there is only one electron in the last orbit of any atom, that can also be separated easily. This separated Electron is called ‘Free Electron’. And the Free electron can move from one atom to the other very easily, and also because of this Free Electron, current flows in all the conductor wires.

Now the question arises as whether in all the conductor wires, can these Free Electrons flow in the same velocity. In other words, the same question can be asked as that whether current passing in different wires is of the same velocity. Further that whether same current passes in all the materials. On the bases of common know how, it can be said that current does not flow in the equal velocity in different materials. The scientists have categorized the conductors as of three types:-

Kind of Conductors:

1. Good Conductor;    2. Semi Conductor;     and       3. Bad Conductor.

Good Conductor:

Generally the metals through which, current can flow without an resistance, are called Conductors. In these metals, free Electrons can travel from one atom to the other. Exactly saying, there is no metal on this earth, which does not create any resistance in the flow of current, but the metals that creates less resistance, are considered to be the Good Conductors, but Gold, Silver and Copper are the best conductors. Generally all the metals are good conductors. Practically for conductor wires, Copper is used as it is cheaper in comparison to gold and silver. These days aluminium is used in place of copper being cheaper.

Semi Conductor:

Semi-Conductors stand at the mid-state of conductors and insulators. These have more capacity to resist current than conductors and less capacity than insulators and less capacity than insulators. When these metals are in pure and crystallec form, have too less number of free electrons, hence too less current flows through these. But when some other metal, which contains some very special properties are added in a very small quantity, the number of free electrons g higher. That increases its conductivity. Germanium and Silicon are the Semi conductors. The metals mixed in these are indium and arsenic, which are added according to the requirement

The Semi-Conductors has initiated a revolution in the electronics world. These days Silicon and Germanium Semi-conductors are being used more.

In Silicon there are total 14 Protons in its Neucleus and in three surrounding orbits 14 electrons are rotating. In the first orbit (K) – 2 electrons, in the second (L) – 8 electrons and in the third and the last orbit (M) – 4 electrons are there.

In Germanium there are total 32 Protons in its Neucleus and encircling it there are total 32 electrons in four orbits. In first (K) – 2 electrons, in second (L) – 8 electrons, in third (M) – 18 electrons and in fourth and last – 4 electrons are there.

For preparing any Semi-Conductor device, except Silicon & Germanium, some other susbstances are also used, which are namely, Boron, Aluminium, Gallium, Indium, Phosphorus, Arsenic and Antimony etc.

All these can be divided in two kinds. First are those, which have five electrons in there last orbit, viz., Phosphours, Arsenic, Antimony etc. and other have three orbits viz. Boron, Aluminium, Indium etc.

Now, when any substance which has five electrons in its last orbit, is mixed in any semi-conductor, forms N – type semi-conductor and if in place of it some other substance is mixed, which has 3 elecrtons in its last orbit, then it forms P – type Semi-conductor. Different Solid State components are produced by mixing N – type and P – type conductors.

Bad Conductors:

The metals through which current cannot flow are called Bad Conductors. Where the flow of current is to be seized, bad conductors are used. The last orbit of these metal’s atoms remain complete, hence the electron in its last orbit cannot be freed. Current can not flow being less ‘free’ electrons. The bad conductors are also called insulators. There are some other insulators, which has the capacity to condense the electron charge; these are called di-electrics. Every insulator is not di-electric, but every di-electric is the insulator. Hence the insulators and the di-electrics have different properties. Insulators are put in the electric circuits for blocking current and the di-electrics to accumulate the electric charge.

Flow of Current:

According to the modern definition of Electricity, in any conductor, when electrons flow from one end to the other, is considered as the flow of current. Now a question arises whether this flow of electrons is being generated without any force.

Let consider a tube of glass filled with some balls. Now the balls are in idial state, when any external force is applied to the balls at one end, then the balls start moving and the last ball of other end goes out of the tube and becomes free.

Sane way at the initial state the electrons of the conductor wire remain stretched towards the Neucleus because of the Centrifugal Force. But when electric force is applied at the ends of the conductor wire, the electron of the last orbit becomes free and starts moving freely. Because the electrons are negatively charged, are attracted towards the positively charged end of the battery. This way the electrons go on moving towards the positive end of the battery and to replace them, electrons from the negative end of the battery flow to the other end. In this

Way electrons flow in the conductor wire, and this flow of electrons is called the current, or in other words it is, that the current is flowing in the conductor wire.

Now the question takes place that whet force is working on the electrons, which are out flowing from the negative end of the battery. As it has already been explained that negatively charged electrons travel towards positively charged poles of the battery. When one electron leaves its place, the place left becomes empty. This empty space is called the ‘HOLE’, and is positively charged. Being positively charged, the electron behind it is attracted towards it, and leaves another empty space at his place, i.e. forms a new hole. This way the flow of electrons from –ve to +ve pole and Holes are formed in the reverse order. When these holes reach at the negative end of the battery then from this –ve pole of the battery electrons fill up these Holes because of the force of attraction, and the function continues further.

Types of Current Electricity:

1.     Direct Current, and

2.     Alternating Current

Direct Current: This is such an electric current, whose direction and rating always remain the same. The current we get from the cells or batteries is the perfect example of the Direct Current. In the Direct Current, the flow of electrons is always against the direction of the current. Electrons travel from –ve to +ve pole and the current flows from the +ve to –ve direction. Because D.C. has always the same direction its frequency remains zero.

Alternating Currrent: The electric current whose direction and rating is always changing is called A.C. At one stage it attains its peak rating on the other stage attains its lowest value, and after this, the same action take place in the reverse order. Because it runs in both the directions, its graph gets the shaper of a wave. In A.C., in one second we get 50 waves, thus the frequency of A.C. comes to be 50 cycles per second. In A.C. because 50 c/s are received in one second, its rating per second would become zero for 100 times, but as this speed is much more than our normal eye vision (16 figures per second), hence we can not see its impact. One pole of A.C. is called Phase and the other one is called Neatural.

A.C. is considered to be better in both the currents, because of its utility. Hence its use is also increasing day by day. There are so many factors which make it more significant. The major cause of it is that we can increase or decrease it according to our need by using a Transformer, where in D.C. it is not possible. Also the shocks of D.C. are much dangerous than that of A.C.

Electric Generators:

To convert Mechanical energy into Electrical energy, the device used is called ‘Generator’. Both A.C & D.C can be generated by the Generator. The Generator that generate A.C. are called A.C. Generators and the Generators that generate D.C. are called D.C. Generators. Here it is to be noted that A.C. can be generated by the Generator only whereas D.C. can also be produced by the chemical process.

The Electric Generators, which work on the Electro-Magnetic principle was invented by Michale Ferade. He pointed out that when a coil of a conductor wire is rotated in a magnetic field, it develops property of electricity in the coil, and as and as the coil rotates, the direction of the electric current produced also changes.

Three Main Features of Electricity:

When the current is flowing in a conductor wire, three main impacts can obviously be observed, which are:-

1. Electric Pressure,     2. Electric Current, and3. Electric Resistance

Electric Pressure:

To induce movement of the electrons in the conductor wire, the force required is called electric pressure or Electo-Motive Force. The difference of Potentials of two charged polarities is called the ‘POTENTIAL DIFFERENCE’. The unit to measure potential difference (p.d.)is VOLT. The higher and the lower units of the volt are as below:

1000 micro volt (mv) = 1 mili volt (mv)

1000 mili volt (mv) = 1 volt (v)

1000 volt (v) = 1 kilo volt (Kv)

1000 Kilo volt (Kv) = 1 Mega volt (Mv)

To measure the potential difference, Volt Meter is used and is always put in the electric circuit in parallel to the load.

Electric Current:

The flow of Electrons in a conductor wire is called Electric Current. When the electrical potential is created at the ends of the conductor wire, the flow of current takes place. It is to be noted, electronic potential is a different phenomenon than that of electric current. This difference can well be recognized by the following example. As the water stored in a tank, lays pressure on the base of the tank which compels the water to flow out. The laid pressure and the out flow of water are two different actions. Now as two actions are two different things, in the same manner, the Electric Potential and the Electric Current are two different phenomenons.

To measure current, the suggested unit is ampere. The other higher and lower units of Ampere are as under:-

1000 Micro Amp. (A) = 1 Mili3Amp. (mA)

1000 Mili Amp. (mA) – 1 Ampere (A)

1000 Ampere (A) = 1 Kilo Ampere (KA)

To measure the current, Ampere Meter is used and it is put in the series to the load in the electric circuit.

Electric Resistance:

The resistance created in the path of electric current by the conductor wire is called ‘Electric Resistance’. All the conductor wires, may be made of any good conductor substance, has the property of restivity upto some extent atleast. This Electric Resistance was discovered by a German Scientist, George Simon Ohm. At his name the unit of Resistance is called ‘Ohm’.

1000 Ohm – 1 Kilo Ohm

1000 Kilo Ohm – 1 Mega Ohm

Ohm meter is used to measure the resistance.

Multimeter:

The single meter by which Electric Potential (V), Electric Current (C), and the Electric Resistance (R) can be measured, is called the Multimeter.

Ohm’s Law:

Ohm’s Law is the theoretical foundation of Electricity. This law was propagated by George Simon Ohm, hence it is called OHM’S LAW.

According to this law, when in any electric circuit (keeping the resistance constant), the electric potential is increased, the rate of flow of current is increased. And also that (keeping the electric potential constant) if the resistance is increased, the rate of flow of current is decreased.

The following three formulae can be derived on the bases of Ohm’s Law:

Volt = Current x Resistance. V = I x R Current = Volt / Resistance. I = V / R Resistance = Volt / Current. R = V / I (Here, I stands for current, V stands for Volt, R Stands for Resistance). If the

value of any two of the three (V,I,R) is known, the third can be detected.