Basic Theory of Science:
So let us have the overview of some basic theories of
science which you may already know, or some of you will study further in your
upcoming classes as you grow up. These basic theories will be somewhere used in
understanding the things ahead.
Energy
To do any work first thing required is energy.
There are different forms of energy like electrical energy, chemical energy,
mechanical energy, light energy, magnetic energy, sound energy and heat energy
etc. Energy cannot be created nor destroyed; it only converts from one form to
another. So anything which has capability in it to do some work is said to have
energy.
- When you turn ON a battery operated torch, the chemical energy inside the battery converts into electric energy due to which small electric current flow through the torch bulb and it converts that energy into light energy. The light changes its surrounding by enlightening it.
- When you switch ON a light bulb, it converts electric energy to light energy and some heat energy due to which the bulb gets little hot apart from generating light. Again the light changes its surrounding by enlightening it.
- When you turn on your fan, it converts electric energy into mechanical energy by rotating its blades which throw air. The airflow changes the environment and lowers the temperature.
- If you play your music system, the speakers converts the electrical energy into sound energy. The sound energy travels in air and reaches your ear drum which vibrates and send the signal to brain hence you can listen to that music.
- When you turn on the water heater, the electric energy is converted into heat energy and it then heats up the water in the geyser.
- Once you start your car or any vehicle, the petrol in the tank which is having chemical energy stored in it, burns and converts into heat energy, which is then converted into mechanical energy inside the engine and hence you can move from one location to other. At the same time there is small electric generator inside every vehicle which rotates using the same mechanical energy and generate electricity which charges the battery in the vehicle and lights the head lamp, tail lamp etc. And this electric energy plays an important role to create spark in engine which ignites the fuel i.e. petrol/diesel. So a vehicle uses chemical, and generate electrical, heat and mechanical energy for its complete functioning.
- When you speak in front of a microphone of your mobile phone, it converts sound energy coming from your vocal cord to electric which is processed by mobile circuit and transmitted through air using electromagnetic waves to nearest tower and then further it reaches to your friend whom you are talking to.
- In a solar panel, light energy is converted into electrical energy which is a free form of energy.
Atom:
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| Atom |
All
maters around us are made of basic building blocks called atoms, and if we
further look into atoms it has electron, proton and neutron. At higher studies
you will learn more details of the atoms structure. Electrons are negatively
charged, protons and positively charged and neutrons are neutral i.e. they are
neither positive nor negative in nature.
Proton
and neutron are at the center of the atom called nucleus and the electrons
revolve round the nucleus in different orbits as our planets revolve around the
sun.
Electric Conductor:
Mostly all metals conduct electric current at normal conditions hence are called good conductor of electricity e.g. Copper, Aluminum and Iron wires etc. Most of the good quality wires which are used at our home are made of copper metal. Some low quality cheap wires use aluminum or copper mixed with aluminum or iron etc. The graphite lead inside your pencil also conducts electricity. Normal tap water is also a good conductor of electricity as it has many metal impurities dissolved in it which help in conducting electricity. If these metallic impurities are somehow removed from water, it will not be able to conduct electricity. More the impurities the better it conducts electricity. I hope you remember the scene from movies “3 Idiots”. Good quality distilled water which we use in our inverter batteries are free from these impurities. You may further study how distilled water is made by evaporating water and then condensing the vapor. But for now, we will restrict ourselves not to go more in deep.
Electric Insulator:
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| Wire |
There are many matters (mostly non-metals) which
do not conduct electricity like, plastic, rubber, dry wood, dry paper and dry
cloth. Why I am mentioning here DRY
word, because if they are wet with water, they will start conducting
electricity as water is a good conductor of electricity as we learned before.
So, if you see any wire, it comes in different colors like Red, Green, Black,
Blue and Yellow etc. These color layers are made of insulating materials like
rubber, plastic etc. and the actual metal wire is inside this insulating layer
to protect these wires from touching each other, else will create short circuit
which results in fire. These insulating layers also protect us from getting
electric shock while handling them.
Difference between Conductor and Insulator:
If All matters are made of atoms which
consist of electron, proton and neutron and as we saw electric current is
nothing but flow of electrons, then why a conductor conducts electric current
but an insulator don’t. The answer is the electrons of conductors are loosely
bonded with their nucleus hence they move easily but in case of insulating
materials, the electrons are bonded to their nucleus very tightly hence they
don’t flow hence do not conduct electricity at normal condition. But any
insulator can also conduct electricity at certain surrounding conditions, but
that we will not learn at this stage. A simple example can be taken around you
is that air doesn’t conduct electricity at normal condition, but when very high
voltage is applied in the spark plug of scooter, bike or car, they create a
spark in the small air gap in the plug. Similarly we see lightening in sky
during rainy season, where a very big electric spark is seen between two bunches
of clouds or between cloud and earth.
Semiconductors:
Materials having electrical conductivity between
conductors and insulators are termed as semiconductors. Silicon and germanium
are most common elements used as semiconductor. Further these elements are
doped or mixed with some other elements to create two types of material called
P-Type and N-Type. This doping can be simply understood as adding impurity in
silicon to alter its conductivity.
Sensors:
Anything which can sense the surrounding environment and
can convert it into electrical energy is called sensor. Surrounding conditions
include temperature, light, sound, humidity, pressure, speed etc. Microphone is
a sensor which sense sound energy and convert to electric energy. Temperature
sensor in electronic thermometer senses your body temperature and converts in
electric signal which is then processed and displayed as digits.
Transducer or Actuator:
Device which can convert electrical energy
into any other form of energy like light, sound or mechanical energy is called
a transducer. They change the surrounding environment around it when they come
in action. So transducer or actuators behaves exactly opposite to sensor. When we power ON a light bulb, it changes its
surrounding i.e. darkness is filled with light. If a fan is turned ON, it
converts electric energy into mechanical energy, which rotates its blade and
throws air to reduce the temperature in the room.
Voltage:
It is an electrical force which pushes the charges in any
conductor to move from higher potential to lower potential. It is also called
as Electromotive Force (EMF). It is measured in unit called volt or denoted as
‘V’.
Current:
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| Electric Current |
The rate of flow of charge from a region in any conductor
is called current or electric current. It is measured in Amperes and denoted as
‘A’. Current is basically flow of electron in any conducting wire when a
potential difference is applied across it. The diagram shows that there is a difference in
potential between two terminals of battery, one terminal is at 12V and other is
at 0V, that is why the current flow in the wire passing through the lamp and the
lamp glow to convert electrical energy into light energy.
Electric Field:
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| Add caption |
There is always a field surrounding any charge (positive
or negative) which applies some force on any other charge if it comes within
this field. Similar charges repel each other and opposite charges attract each
other. Any moving charge denotes a current and this creates a magnetic field
around the wire through which the current is flowing. Direction of magnetic field
depends on direction of current flowing through the conductor.
Magnetic Field:
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A magnet has two poles i.e. north and south. A magnet is also surrounded by a field which
exerts force on any magnetic material like iron. Any other magnet which comes
in the area of this field is either attracted or repelled based on direction of
poles. Similar poles repel each other and opposite poles attract each other.
This area surrounding a magnet is the magnetic field. Any magnetic compass if
brought in this field will deflect according to the direction of field at that
location.
Electrical and Magnetic Rules:
Any wire carrying electrical current produces a magnetic field around it and the direction of magnetic lines of forces depend on the direction of current flowing through the wire. If we consider a straight wire carrying current holding in hand as in picture, where the thumb shows the direction of current flowing through the wire then the direction of magnetic lines of forces will be in the direction in which our remaining four fingers are curled naturally. Similarly, if the direction of current is reversed, the direction of magnetic lines of forces will reverse. Think of holding the same wire in reverse as if your thumb now points downwards and then observer in which direction your rest four fingers get curled.
So, this magnetic field around and current carrying conductor interact with any other nearby magnetic field. Depending upon the direction of both magnetic fields, either both will attract each other or repel each other.
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| Motor |
Similarly if any wire is moved along magnetic field so that it cuts the magnetic lines of forces, an electric current is induced in the wire. The direction of flow of current depends on direction of magnetic fields and the direction of movement of wire. This is defined by “Flemings Right Hand Rule”. This property is used in functioning of Electric Generator. A coil is attached to shaft of generator and this coil is inside a magnetic field. When the shaft is rotated by some mechanical means externally, the coil rotates inside magnetic field which cuts magnetic lines of forces and generates electric current in the coil which is used to run electric equipment. Interesting fact is that a small DC motor can work as small electric generator if its shaft is rotated by external means.
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