Electricity
History.
Electric charge.
Voltage.
Current.
Resistance.
Resistivity.
Electrical circuits.
Ohm's law.
Resistors in series.
Resistors in parallel.
Power.
Direct current.
Alternating current.
Electrical energy.
Electric energy genertion.
Electricity in lighting.
Electricity in heating.
Mechanical energy from electrical energy.
Electrical safety.
History.
Human beings were first exposed to electricity, by lightning .
Lightning was feared by human beings.
They thought that the heavens, were expressing anger, with lightning bolts.
Today, we take electricity for granted, as a necessary utility.
Interestingly, the very first experiments, scientists did, involved lightning.
In 1752, Benjamin Franklin, flew a kite, into a strong cloud.
He attached a metal ring, to the string.
Sparks started to fly from the metal ring, to his hands.
Franklin, then went on to develop, some basic theories of electricity.
He came up with the idea, of a positive and negative charge.
Luckily for Franklin, his experiment, drew only small electrical charges, from the cloud.
If the kite, had been struck by lightning, Benjamin Franklin, would have died of shock.
Now that we know, the power of electricity, in lightning,
we never ever, should try this experiment.
Many other scientists, helped in our understanding, of electricity.
Around 1800, Alessandro Volta, developed a rudimentary battery.
For the first time, electricity could be generated.
For his contribution, the unit of voltage, the volt, is named after him.
Charles Augustin de Coulomb, did extensive experiments, with electric charges.
For his contribution, the unit of electrical charge, Coulomb, is named after him.
George Ohm, experimented with different materials, to conduct electricity.
He discovered, that some materials, conducted electricity, better than others.
He developed the concept of resistance.
For his contribution, the unit of resistance, the Ohm, is named after him.
Andre-Marie Ampere, discovered the relationship, of electricity and magnetism.
For his contribution, the unit of electrical current, the Coulomb, is named after him.
James Prescott Joule, proved that electricity, is a kind of energy.
For his contribution, the unit of energy, the Joule, is named after him.
Michael Faraday, invented the electric motor, in 1821, and later the electric generator.
This was a great step forward, for the practical use, of electricity.
Thomas Alva Edison, invented the first practical electric bulb.
This invention, literally lit up the world.
Edison, went on to build the first large scale, commercial electric power plant, in 1882.
Electricity, arrived in our lives.
Before electricity, the major source of power, was manpower.
The pyramids built 5000 years ago, used manpower, in a large scale.
Even the Taj Mahal, built around 300 years back, used manpower.
For thousands of years, manpower was the primary source of energy.
Human beings, supplemented manpower, with animal power.
In a sense, animals were our first machines.
Animals, like the horse, the cow, the camel, the mule, etc., played an important role,
in supplementing manpower.
In fact the unit of power, was measured, in horse power.
Apart from manpower, and animal power, our other source of energy,
was heat from fire.
Use of fire, started with cooking.
We went on to build furnaces.
Early furnaces, were used to burn bricks.
Later, we learnt to use furnaces, to melt copper, and iron.
The copper age, and iron age, bookmarked these periods, in our technological evolution.
Heat was a very useful source of energy.
But heat could not be transported, and distributed.
The heat from our kitchen stove, cannot be used, in the nearby washroom,
to heat our bath water.
We do not consume electricity directly.
Electricity is converted to some other form of energy,
like, light, heat, mechanical power, etc., to be of practical use.
All the machinery, equipment and appliances, that we use,
take in electricity as an input, and convert it to some other form of useful energy.
Perhaps, the greatest advantage of electricity, is the capability of electricity,
to be transported, over long distances.
We can generate electricity in one place, and transport it to another place,
hundreds, even thousands of kilometres away.
This made the generation, and distribution of energy, very practical, and powerful.
Thermal power plants, hydroelectric power plants, nuclear power plants, etc.,
generated electricity, on a large scale.
It is distributed all over the world, and can light up a bulb, in a remote village.
This became so convenient, practical and powerful,
that the major source of energy in the world, today comes from electricity.
Electric charge.
Electricity is basically, the flow of electrons, in a conducting material.
When we say electricity is flowing through a wire,
what we mean is, electrons are flowing through the wire.
An atom, has protons, neutrons and electrons.
The protons, are positively charged particles.
The electrons, are negatively charged particles.
When electricity flows through a wire, electrons flow, from one atom to another,
through the wire.
Some materials, conduct electricity, better than others.
They are called good conductors.
A copper wire, or an aluminium wire, are commonly used,
good conductors of electricity.
Electrons flow from a negative charge, to a positive charge.
A positive charge, is represented with a plus sign.
A negative charge, is represented, with a minus sign.
The amount of charge, is measured with the charge of the electron, as a unit.
An electron, has a charge of minus 1.6022 into, ten to the power of minus 19 coulombs.
In other words, a coulomb is defined as, the charge contained in,
6.241 into 10 to the power of 18 electrons.
For electricity to flow through a wire, one end of the wire, should have a positive charge.
Another end of the wire, should have a negative charge.
A battery, is a source of electrical energy.
In a battery, chemical energy, is converted to electrical energy.
One end of the battery, has a positive charge, marked by a plus sign.
Other end of the battery, has a negative charge, marked by a minus sign.
If we connect, the positive charge end, to the negative charged end,
with a conducting wire, the circuit becomes complete.
Electrons, start flowing in the wire, from the negative charge end,
to the positive charge end.
Voltage.
We will take water as an analogy, to understand some concepts of electricity.
Water is stored in an overhead tank, in our homes.
The water in the tank, has potential energy.
When the tap in our home, is closed no water flows.
When the tap is opened, water flows, from the tap.
The electricity outlet in our home, is a ready source, for electrical energy.
When not in use, no electricity flows.
If we plug in a table lamp, to the electricity outlet, the circuit is completed.
Electricity flows, from one terminal in the outlet, through the lamp,
and back, to the other terminal in the outlet.
The lamp glows.
The electricity outlet, is also called as a plug point.
When we insert an appliance, with a plug, into the plug point,
it draws electricity, from the outlet.
A simple plug point has two terminals.
One point is live, that is, it has a higher potential.
The other point is neutral, and it has a lower potential.
There is an electrical potential difference, between the two points.
It is like the energy of the water, in the overhead water tank.
When not in use, there is no flow.
When we close the circuit, there is a flow of electricity.
The potential difference, which causes this flow, is called Voltage.
The larger the potential difference, the larger is the voltage.
A small AA battery, provides a voltage of 1.5 volts.
A typical car battery, provides a voltage of 12 volts.
A home electricity outlet, has a voltage of 220 volts.
Higher the voltage, higher is the pressure, for the electrical charge to flow.
Voltage is measured, in joules of energy, per coulombs of charge.
One volt, is the potential difference between two points,
that will impart one joule of energy,
per coulombs of charge, that passes through it.
One volt is equal to one joule, divided by one coulomb.
A voltmeter is used to measure voltage.
Current.
When two points, with an electrical potential difference, are connected with a conductor,
electricity, flows through it.
The rate at which, the electricity flows, is called the current.
The unit of measuring current, is the ampere.
The ampere, is defined as the flow of one coulomb, of charge, in one second.
The more the current, the more will be the flow of electrons, or charge.
Ampere, measures the quantum of electrons, or charge flow.
If we take an analogy of a water pipe, water flows through the pipe.
We can measure the rate at which the water flows.
In a conducting wire, the ampere is the measure, of the rate of electron flow.
When the water pipe is larger, we expect more water to flow.
Similarly, when the conducting wire is thicker, we can expect,
more electrons to flow.
A coulomb is the charge of, 6.241 into 10 power 18 electrons.
When one ampere is flowing through a conductor,
6.241 into the power of 18 electrons, are flowing,
in one second through the wire.
If a wire has 5 amperes of current, flowing through it,
it means that 5 coulombs of charge, is flowing in one second, in the wire.
Ampere measures, the rate of flow of electricity.
An ampere is sometimes referred to as amps in short.
An ammeter is used to measure current.
Resistance.
Different materials have different conducting capacity, for electricity.
Materials which offer, very low resistance, to conducting electricity,
are called Conductors.
Copper wire, aluminium wire, are examples of good conductors.
Materials which offer, very high resistance, to conducting electricity,
are called Insulators.
Rubber, plastic, porcelain, are examples of good insulators.
A copper wire, is covered with a plastic sleeve to provide insulation.
This safety feature, protects us from coming into contact with electricity.
The amount of resistance, of a resistor is measured in ohms.
The ohm is the resistance, between two points of a conductor,
when a potential difference, of one volt,
produces a current of one ampere.
One ohm, is equal to one volt, divided by one ampere.
An Ohmmeter is used to measure resistance.
Resistivity.
The resistance value of a resistor,
is dependent on 3 factors.
Resistance is directly proportional, to the length of the material.
A longer wire, will have a higher resistance.
Resistance is inversely proportional, to the cross sectional area,
of the material.
A thicker wire, will provide lower resistance.
If we take the analogy of water, flowing in a pipe,
a longer pipe, will offer more frictional resistance to water flow.
A larger pipe, will allow for freer water flow.
Different materials, have different levels of conducting and resisting capacity,
to the flow of electricity.
Good conductors, have low resisting capacity.
Insulators, have high resisting capacity.
The resisting capacity of a material, is called resistivity.
Resistivity is measured, as Ohms per meter.
The symbol for resistivity, is “Rho”.
Resistance can be expressed as a formula.
Resistance R = “Rho”, multiplied by length, divided by area.
Unit for length is meters.
Unit for area is square meters.
Unit for resistance is Ohms.
The unit of resistivity, “Rho”, is Ohms per meter.
The resistivity of a good conductor, like copper,
is 1.62 multiplied by 10 to the power of minus 8, Ohms per meter.
The resistivity of good conductors, is very low.
But, we should remember, they still offer, some small resistance.
The resistivity of an insulator, like rubber,
is about 10 to the power of 16 Ohms per meter.
We can now imagine, that a conductor, allows the free flow of electrons.
A insulator, tries its best to block the flow of electrons.
Electrical circuits.
The flow of electricity, can be conveniently represented, in a diagram.
Such a diagram, is called a circuit diagram.
The conducting wire, is represented as a line.
A battery is represented, as two parallel lines,
one short, and one slightly longer.
A resistance is represented, by a jagged line.
A switch is represented, by a inclined line, which can be ‘On’, or ‘Off’.
An ammeter, is represented, by the letter ‘A’ , in a circle.
A voltmeter, is represented, by the letter ‘V’ , in a circle.
A positive charge is represented, by a plus sign.
A negative charge is represented, by a minus sign.
The flow of current is represented, by an arrow.
Electrons flow, from the negative charge to the positive charge.
In electrical circuits, we however use the convention of flow from positive to negative.
This is only a convenient convention.
The value of current, in amperes, is represented as ‘I’.
The value of voltage, in volts, is represented as ‘V’.
The value of resistance, in Ohms, is represented as ‘R’.
We can connect, a 12 volt battery, to a 10 Ohm resistor.
A conducting wire, connects the resistor, to the battery, via a switch.
A ammeter, connected to the wire, measures the current.
A voltmeter connected, across the battery, measures the voltage.
Now, we are ready to go.
When we set the switch to on, the circuit is complete.
The voltage ‘V’ causes, a current ‘I’, to flow through the circuit.
The current from the battery, flows to the resistor, and back to the battery.
Ohm’s law.
Ohms law states, that the current through a conductor, between two points,
is directly proportional to the potential difference across the two points.
The current ‘I’, is proportional to the potential difference, or the voltage, ‘V’.
We can state Ohm’s law as,
voltage=current multiplied by resistance.
’V’, = ‘I’, multiplied by ‘R’.
We can also say, ‘V’ = ‘I’ , ‘R’.
’V’ is the voltage, in volts.
’I’ is the current, in amperes.
’R’ is the resistance, in Ohms.
This simple formula can be extensively used,
in most of our calculations, involving electricity.
In the circuit diagram, we just discussed, the voltage of the battery, is 12 volts.
The value of the resistance, is 10 Ohms.
Using the formula, ’V’, = ‘I’, multiplied by ‘R’,
we can calculate the current ‘I’.
’I’, = 12 divided by 10, is equal to 1.2 amperes.
A current of 1.2 amperes, is flowing through our circuit.
We can do experiments with these circuits.
Let us increase the resistance, to 20 Ohms.
The current now will be, 12 by 20, equal to, .6 amperes.
Let us decrease the resistance, to 5 Ohms.
The current now will be, 12 by 5, equal to, 2.4 amperes.
We can conclude, that given a voltage,
increasing the resistance, reduces the current,
reducing the resistance, increases the current.
We can also experiment, by varying the voltage.
Let us replace the 12 volt battery, with a 6 volt battery.
Resistance is 10 Ohms.
Current is equal to 6 by 10, is equal to .6 amperes.
Let us use a 24 volt battery.
Now, current is equal to 24 by 10, is equal to 2.4 amperes.
We can conclude, that for the same resistance,
decreasing the voltage, induces a smaller current.
Increasing the voltage, induces a larger current.
Even as we go on to study, more complex electrical circuits,
the basic principles, of Ohms law, will still hold good.
Resistors in series.
The electrical circuit we discussed, had a battery, a resistor,
an ammeter, a voltmeter, and a switch.
We can extend this circuit, by adding two resistors in series.
That is, the resistors are added to the same path, of the circuit.
The first resistor, has a resistance of ‘R1’, equal to 2 Ohms.
The second resistor, has a resistance of ‘R2’, equal to 4 Ohms.
A 12 volt battery, provides a voltage, of ‘V’, equal to 12 volts, in the circuit.
Since it is a single circuit, the current flowing, through the circuit will be the same, say ‘I’.
The same current ‘I’, flows through both the resistors.
When 2 resistors, ‘R1’, and ‘R2’, are connected in series, the effective resistance,
’R’, is equal to the sum of both the resistances.
In this case, ‘R’, is equal to ‘R1’, plus ‘R2’.
’R’, is equal to 2 Ohms plus 4 Ohms, equal to 6 Ohms.
’V’, is equal to ‘I’, into ‘R’.
Battery voltage, ’V’, is equal to 12 volts.
Effective resistance, ’R’, is equal to 6 Ohms.
’I’, is equal to ‘V’, by ‘R’, equal to, 12 by 6, equal to 2 amperes.
The same current of 2 amperes, flows through both the resistors.
We can calculate the voltage, across each resistor.
The voltage ‘V1’, across the resistance ‘R1’, will be ‘I’, into ‘R1’.
”V1”, is equal to 2 amperes, into 2 Ohms, equal to 4 volts.
The voltage ‘V2’, across the resistance ‘R2’, will be ‘I’, into ‘R2’.
”V2”, is equal to, 2 amperes into 4 Ohms, equal to 8 volts.
In such a circuit, the total voltage, or the battery voltage,
is equal to the sum of the voltage, across the two resistors.
’V’, is equal to ‘V1’, plus ‘V2’.
In our case, ‘V’ is equal to 4 volts, plus, 8 volts, equal to 12 volts.
To summarise, when resistors are connected in series:
The current flowing, through all the resistances, is the same.
The effective resistance, is the sum of all the resistances, of all the resistors.
The voltage across, each resistor, is current ‘I’, into the resistance value, of the resistor.
The sum of the voltage, across each resistor, is the supply voltage.
The same principle, holds for any number of resistors,
say, ’n’, resistors, connected in series.
Effective resistance ‘R’, equal to ‘R1’, plus ‘R2’, plus ‘R3’, up to, plus ‘Rn’.
Total voltage, is equal to ‘V1’, plus ‘V2’, plus ‘V3’, up to, plus ‘Vn’.
Festival lights, are an example of a large number of resistances,
connected in series.
Resistors in parallel.
Two resistors, can be connected in parallel, in the circuit.
When two resistors are connected in parallel, the current has two path ways, to flow.
The current flows, through both of them.
When two resistors, ‘R1’, and ‘R2’, are connected in parallel,
the effective resistance, ‘R’, is given by the equation,
1 by ‘R’ is equal to, 1 by ‘R1’, plus, 1 by ‘R2’.
Let ‘R1’ be equal to 6 Ohms.
Let ‘R2’ be equal to 3 Ohms.
1 by ‘R’, will be equal to 1 by 6, plus, 1 by 3, equal to 6 by 12, equal to 1 by 2.
1 by ‘R’, is equal to, 1 by 2.
’R’ is equal to 2 Ohms.
It is interesting to note, that when two resistors are connected in parallel,
the effective total resistance, decreases.
When 6 Ohms, and 3 Ohms, are connected in parallel,
the effective resistance, decreases to 2 Ohms.
The voltage, across both the resistances, ‘R1’ and ‘R2’, will be the same.
’V’ equal to 12 volts, for both ‘R1’, and ‘R2’.
Now the current has two path ways, to flow through.
The current branches out, and a part of it flows through, ‘R1’.
The other part, flows through ‘R2’.
We can apply Ohms law, to both the resistors.
The current flowing through ‘R1’, is equal to ‘V’ by ‘R1’.
”I1”, is equal to ‘V’, by ‘R1’, is equal to 12 by 6, is equal to 2 amperes.
The current flowing through ‘R2’, is equal to ‘V’, by ‘R2’.
”I2”, is equal to ‘V’, by ‘R2’, is equal to 12 by 3, is equal to 4 amperes.
The total current ‘I’, is equal to ‘I1’, plus ‘I2’.
”I”, is equal to 2 amperes, plus 4 amperes, is equal to 6 amperes.
We can also calculate the current, using the effective resistance.
The effective resistance of this parallel, resistor circuit, is 2 Ohms.
Applying Ohms law, ‘I’, is equal to ‘V’, by ‘R’, is equal to 12 by 2, is equal to 6 amperes.
We can visualise this, by imagining, two pipes in parallel.
2 amperes flow through the resistance of 6 Ohms.
4 amperes flow through the resistance of 3 Ohms.
Total flow of current, is 6 amperes.
The same principle, holds for any number of resistors,
say, ’n’, resistors, connected in parallel.
We can summarise, the properties, of ’n’, resistors connected in parallel:
The voltage across all the ’n’, resistors, will be the same, ‘V’.
The effective resistance, is given by,
1 by ‘R’ is equal to, 1 by ‘R1’, plus, 1 by ‘R2’, plus, up to, 1 by ‘Rn’.
The current ‘I’,’n’, flowing through resistance ‘Rn’, will be ‘V’ by ‘Rn’.
The total current, ‘I’, is equal to ‘I1’, plus ‘I2’, plus, up to ‘I’,’n’.
Power.
Power is the energy, consumed per unit of time.
Electrical power, is equal to voltage multiplied by current.
’P’, is equal to ‘V’, multiplied by ‘I’.
Unit of voltage, is joules per coulomb.
Unit of current, is coulombs per second.
Power is equal to ‘V’, into ‘I’,
is equal to joules per coulomb, multiplied by coulombs per second,
is equal to joules per second,
which is the unit of power.
One joule per second, is equal to one watt.
Power is measured in Watts.
In our electrical circuit, we had a voltage of 12 volts,
and a current of 1.2 amperes.
The power consumed in this circuit,
is 12 volts multiplied by 1.2 amperes, equal to 14.4 watts.
We can also, use the equation for power in different ways, using Ohms law.
’P’, is equal to, ‘V’, into ‘I’.
By Ohms law ‘V’, is equal to, ‘I’, divided by ‘R’.
substituting ‘I’, by ‘R’, for ‘V’,
’P’, is equal to ‘I’, squared ‘R’.
So far, we have been using examples, of battery voltage.
The power we get from the main supply, in our homes,
is standardised to 220 volts.
The same Ohms law, and the power equation applies to any voltage,
including the mains voltage, of 220 volts, in our homes.
Let us work out a few examples, with 220 volts.
A hundred watt bulb, is connected, to a 220 volt outlet.
’P’, is equal to ‘V’ into ‘I’.
It will draw 100 watts, divided by 220 volts, equal to, .45 amperes.
A 2200 watt, electrical heater, will draw,
2200 watts, divided by 220 volts, equal to 10 amperes.
The higher the power rating, or the wattage, the higher is the current drawn.
Direct Current.
Direct current, is also referred to as DC current.
Direct current, is what we get from a battery.
In Direct current, the voltage is constant, with time.
If we plot Time in the X axis, and Voltage in the Y axis,
DC current, will have a straight line, parallel to the X axis.
The co-ordinate of the Y axis, is the voltage.
DC current, is used in electronic devices.
DC current, used in electronic devices, has a low voltage.
Typical electronic devices use, 3 to 12 volts, of DC current.
Mobile phones, TV, Computers, etc., are examples of electronic devices.
Control mechanisms, of many machinery, and electrical appliances,
are also examples of electronic devices.
For example, the control mechanisms in refrigerators, air conditioners,
microwave ovens, washing machines, are electronic devices.
The supply voltage we get, from our electricity provider, is alternating current.
It is also called AC current.
The supply voltage, is 220 volts.
Electronic appliances, and control mechanisms, require low voltage DC current.
The voltage, of 220 volts, can be reduced, to the required low voltage,
using transformers.
AC current, can be converted to DC current, using rectifiers.
Using transformers and rectifiers, 220 volt AC current can be converted,
to low voltage, DC current.
This is what is done, to power our electronic devices, in our homes,
and even in Industry.
Our computer for example, takes in 220 volt, AC current,
but actually works in low voltage, DC current.
This is true, for many other electronic devices.
In practice, we use a mix of AC and DC current, for both commercial,
industrial, and residential use.
Alternating current.
In alternating current, or AC current,
the voltage, changes with time.
If we plot, Time on the X axis, and Voltage on the Y axis,
the graph will represent a sinusoidal wave.
That is the voltage, will increase to a peak, then drop down to a low value,
and again increase, to a peak high value.
This pattern, resembles a wave.
A sine wave form, is cyclical.
The cycles, repeat itself.
The number of cycles, in a second,
is called as the frequency of the wave.
The frequency, is measured in hertz.
One hertz, is equal to one cycle per second.
The supply voltage that we get, has a frequency of 50 hertz,
which represents, 50 cycles per second.
World wide, electricity providers, supply AC current.
This is due to, some practical, and historical reasons.
Usually, electricity is generated, at a large power plant,
and distributed to users, over large distances.
Electricity is distributed, by electric transmission wires.
These wires are good conductors.
They have low resistivity.
But total resistance, is also proportional, to the length of the wire.
The total resistance of the long wire, becomes significant.
Power is equal to, ‘I’ squared, ‘R’.
Power consumed, is proportional to the square of the current, ‘I’.
When electricity is transmitted over long distances,this power is dissipated, as heat.
This power is lost.
Over long distance electricity transmission, this loss of power,
is called as transmission loss.
To minimise transmission losses, electricity is transmitted, over long distances,
at a high voltage.
Typically, this will be thousands of volts.
If we look at Ohm’s law,
’V’, = ‘I’, ’R’.
For the same resistance, very high voltage, results in very low current.
Power, ‘P’ = ‘I’, squared, ‘R’.
When the current is very low, the power loss is also very low.
This is the reason AC transmission, over long distances,
is done at a very high voltage.
The supply voltage, in Industry and homes, is 220 volts.
Transmission voltage, is in thousands of volts.
A great advantage, of AC power, is that the voltage,
can be stepped up,
or stepped down, using transformers.
At the generating station, the voltage is stepped up,
using, step up transformers.
The transmission takes place at high voltage.
When the transmi wire, reaches a city, the voltage is stepped down,
in a sub station, using step down transformers.
The voltage is further stepped down, at the local level, to 220 volts.
The ability to easily, step up and step down voltage,
combined with the low power losses, of long distance transmission,
made AC, the preferred standard, world wide,
for generating and consuming, electricity.
Most of the electricity generated from large power plants, connect to a power grid.
From the power grid, electricity is distributed to,
industrial, agricultural, commercial, and residential users.
Electricity transmission and distribution, is done by electricity supply companies.
We can also generate electricity locally.
For example, roof top solar panels, can generate electricity.
This can be fed to power grid, of the electricity supply company.
A two way meter, can be used for this purpose.
Depending on supply and need, local production of electricity,
can be given to the grid, or drawn from the grid.
This trend is likely to increase, in the future.
Electrical energy.
Electric power is measured in Watts.
A thousand Watts is 1 kilo watt.
Electrical energy consumption, is measured in kilo Watt hour.
One kilo Watt hour, or KWH is also commonly called as 1 unit of energy.
Electricity companies charge us, on the number of units of electricity,
that we consume.
Electrical energy consumption, can be easily calculated.
A hundred Watt bulb, used for 10 hours,
consumes hundred into ten, equal to, one Kilo Watt Hour, or one unit of electricity.
A two kilo Watt hot plate, used for 5 hours, will consume 10 KWH, or 10 units.
The electric meter in our homes, measure the cumulative consumption,
of all the appliances, in our home.
Our electricity bill, is generated based on the cumulative unit consumption.
We do not consume electrical energy directly.
We convert electrical energy to some other form of energy,
and put it to some practical use.
Electrical energy can be converted to heat energy, or kinetic energy,
or other forms of energy.
This is one of the major advantages, of electrical energy.
We can have one source of energy, and conveniently convert it to,
another form of energy, useful to us.
For example, we use a hot plate, to generate heat energy, from electrical energy.
Electric energy generation.
Electrical energy, is the largest source of energy consumption in the world.
About 5 terra Watts, of electrical energy is generated in the world.
Electric energy, is the most popular form of energy, in the world.
There are good reasons for this popularity.
It can be generated in one physical location,
and distributed to consumers, in a vast geographical area.
Electrical energy can be easily converted to other forms of energy.
For example, it can be converted to heat energy, mechanical energy, etc.
Electricity is supplied in a standard way.
Typical supply voltage is standardised as 220 volts,
at a frequency of 50 Mhz.
Most of the machinery, and appliances, can be manufactured,
in a standardised way, to use this source of energy.
If we look around our home, most of the appliances,
work with standard electricity, from the supply company.
Industrial and commercial establishments, also use standard electricity.
This standardisation makes electricity, a very practical economic,
way of using energy.
The economic progress, of a country, can often be judged,
by the per capita production of electrical energy.
Much of the electrical generation, is done through combustion of fossil fuels,
like coal, and natural gas.
The most commonly used fossil fuel is coal.
Coal is burnt, to create heat energy.
The heat energy is typically used to generate steam.
The steam drives a turbine, to generate mechanical energy.
The turbine drives a generator.
The generator uses electromagnetic forces, to generate electricity.
Fossil fuels are finite, and exhaustible source of energy.
It is also highly polluting.
Combustion of fossil fuels, is the largest source of carbon dioxide emission.
Carbon dioxide emission, is a major factor, in global warming.
Countries are working together, to reduce carbon dioxide emission.
Hydro electric energy, is another major source, of electrical energy.
Water is stored, in large dams.
When this water flows out, it drives a turbine.
The turbine drives, a generator, which produces electrical energy.
Nuclear energy, is a newer source of electrical energy.
Nuclear reactors, use fissionable elements, like Uranium and Plutonium.
Uranium and Plutonium, undergo radio active decay.
This is used to produce a nuclear chain reaction.
This nuclear reaction, produces energy.
This energy is used to generate heat energy,
which is used to produce, electrical energy.
Nuclear energy production does not pollute the atmosphere.
Nuclear reactors are potentially dangerous, and great care, needs to be taken,
to prevent nuclear accidents.
Nuclear waste, gives out radiation, which is harmful.
Recycling or disposing, nuclear waste, poses a technological challenge.
Scientists are working, on finding better ways, to recycle,
or dispose nuclear waste.
Wind energy, is a source of renewable energy.
Wind power, is used to rotate turbines.
This can drive a generator, to produce energy.
In places where wind energy is substantial, wind mills can be used, to generate electricity.
Solar energy, is possibly, the most promising form of renewable energy.
Solar radiation or light, is omnipresent.
It is available everywhere.
Photovoltaic cells can be used, to convert solar energy, to electrical energy.
Solar panels, are array of photovoltaic cells.
They can be installed anywhere.
Solar energy can be produced, in a small or large installation.
We can even have a rooftop solar panel.
We can install solar panels, in remote villages, which have no access,
to conventional electricity.
Solar energy is very clean, it does not produce any pollutants.
Unlike fossil fuels, which is exhaustible, solar energy is abundant, and inexhaustible.
Electricity in lighting.
Electricity is the most common energy, used for lighting.
Electrical energy is converted to light energy, to provide light.
The traditional electric light, was an incandescent lamp, or bulb.
An incandescent lamp, has a thin tungsten filament, enclosed in a glass shell.
The inside of the bulb, is a vacuum.
That is all the air inside is evacuated, and tightly sealed.
The tungsten filament, is very thin, and is coiled, to give it more length.
When electricity flows through it, the filament offers resistance.
This resistance causes the filament to heat up, and glow.
The glow is what, gives us light energy, from the incandescent lamp.
If there was any oxygen, inside the lamp, the filament will burn up.
This is why the air is evacuated, and vacuum created, inside the bulb.
If we touch the bulb, which has been lit for sometime, it will be very warm.
This is because of the heat energy, emitted by the filament.
The heat energy, is wasted energy.
Though incandescent lamps, were the most widely used, source of light,
they are very energy inefficient.
The lumen, is a unit of measuring light energy.
Incandescent lamps, produce about 15 lumens, of light energy,
per watt of electrical energy.
A typical incandescent lamp, has a power rating of 60 watts.
Fluorescent lamp is filled with mercury vapour.
The fluorescent lamp, can be in the form of a tube,
sometimes called as a tube light.
When electricity passes through it, the mercury vapour gets excited.
It emits ultra violet light.
The inside of the glass shell, is coated with phosphor.
The ultra violet light, causes the phosphor coating to glow.
This gives us the required visible light.
Fluorescent lamps, are much more energy efficient.
If we touch a fluorescent lamp, it will not feel warm.
This means that the waste heat energy, is minimised in this type of lamp.
Fluorescent lamps, are now available is smaller sizes,
and are called compact fluorescent lamps, or CFL bulbs.
A typical CFL lamp, has a power rating, of 18 watts.
Mercury is a poisonous substance.
We should take care to recycle, or scientifically dispose of used CFL lamps,
to prevent pollution of the environment.
Light can also be produced, by a semi conductor, light emi diode.
They are commonly called as LED bulbs.
LED bulbs are widely used, as indicator bulbs, in many appliances.
We can find them in mobile phones, TVs, washing machines, microwave ovens, etc.
The process by which LED lamps, convert electrical energy, to light energy,
is called electroluminescence.
LED lamps are highly energy efficient.
There is very little wasted energy.
An single LED lamp, produces low intensity light.
It is useful as an indicator lamp.
An array of LED lamps, can produce more light.
It can be used for domestic and commercial purposes.
LED is the most energy efficient form, of lighting.
It is capable of producing more than 100 lumens of light energy,
per watt of electrical energy.
In future, we can expect increased use of LED lighting.
Electricity in heating.
Producing heat energy, is another common use of electrical energy.
A water heater, an electric oven, an electric iron, a room heater, an electric furnace,
are examples, where electrical energy is converted to heat energy.
A electric Iron has a heating element.
A heating element offers resistance, to flow of electricity.
This resistance causes it to heat up, when electricity flows through it.
This heat, is then transferred to the clothes we are ironing.
We can adjust, the amount of heat, that the electric Iron produces.
This can be done, by varying the resistance.
Let us take an example.
An electric iron has a resistance of 110 Ohms.
Voltage supply is 220 volts.
We know that ‘V’, = ‘I’, ‘R’.
The current drawn is, 220 divided by 110, equal to 2 amperes.
Power is equal to ‘I’ squared, ‘R’.
So, the electric Iron consumes, 2 squared, multiplied by 110, watts.
This is equal to 4 into 110, equal to 440 watts, of power.
This will produce, relatively less heat, suitable for certain kind of dresses.
We will now change, the resistance to 55 Ohms.
‘V’, = ‘I’, ‘R’.
The current drawn, is 220 divided by 55, equal to 4 amperes.
We note that a lower resistance, is drawing more current.
Power is equal to ‘I’ squared, ‘R’.
We note, that power consumption, is proportional to the square,
of the current drawn.
Power consumption in this case will be, 4 squared into 55.
This is equal to 16 multiplied by 55, equal to 880 watts.
This higher wattage, will produce more heat.
This heat may be required for certain kinds of dresses.
Mechanical energy from electrical energy.
One of the most useful forms of energy, is mechanical energy.
Many appliances in our home, use mechanical energy.
Some examples are the fan, the mixer, the washing machine, the water pump,
the elevator, the compressor in the fridge, etc.
Most of industrial machinery, also use mechanical energy.
Printing machines, cu machine, cranes, machine tools, etc.
are examples of industrial machines, which use mechanical energy.
The electric motor, is the most commonly used device,
to convert electrical energy, to mechanical energy.
The fan uses an electric motor, to rotate the blades,
which results in circulating the air.
The mixer uses an electric motor, which rotates the blades,
resulting in grinding the ingredients.
The washing machine uses the electric motor, to rotate the drum,
which helps to wash the clothes.
A electric motor, drives a pump, which pumps up water,
from the sump, or the bore well, to the overhead tank.
A crane uses an electric motor, to lift heavy weights.
An elevator, uses an electric motor, to transport us from floor to floor.
A electric motor uses, electro magnetic principles,
to convert electrical energy, to mechanical energy.
When electricity flows through the coils, in the motor, it induces a magnetic field.
The interaction of the induced magnetic field, with stationery magnets,
results in rotating the shaft in the motor.
The rotary motion can be used as mechanical energy,
like in a fan, mixer, or washing machine.
The rotary mechanical energy, can also be converted to other forms of energy.
In many appliances, and machineries, energy is converted, from one form to another.
In a water pump, mechanical energy, is converted to potential energy,
stored in the water, in the overhead tank.
In a fridge, what starts out as mechanical energy, finally results,
in transfer of heat energy.
In a fridge, a electric motor, drives a compressor.
The compressor, compresses a refrigerant.
The compressed refrigerant, passes through an evaporator.
When the refrigerant evaporates, it absorbs heat.
The heat absorbed, is proportional, to the latent heat of evaporation,
of the refrigerant.
The evaporating refrigerant, absorbs the heat, inside the fridge.
The refrigerant then passes through, coils outside the fridge.
The ambient air, around the coils, outside the fridge, absorb the heat.
Heat is thus transferred, from inside the fridge, to the surroundings.
If we keep our hand, behind the fridge, we can feel the heat, that has been transferred.
Electrical energy, is the most convenient way, to source a standard form of energy,
and convert it to, any other form, that we require.
Electrical safety.
Electrical energy, is the most useful, and widely used form of energy.
Electricity from a low power, AA battery cell, is not dangerous.
Supply energy, which is high power energy, is dangerous.
If we come into contact, with high power electricity, it is very harmful,
and potentially fatal.
Rubber is an good electrical insulator.
If we wear rubber gloves, and rubber boots, it can provide us protection,
from unwanted electrical shocks.
Industrial workers, working in electrically hazardous environment do this.
It will be impractical for us, to always do so.
However, it might be a good practice, to wear insulating material,
before touching, a suspect electrical appliance.
Many safety measures, are adopted, to protect us, from harmful effects of electricity.
All manufacturers of electrical appliances, and machinery, take great care,
to ensure that, we do not directly come into contact, with electricity.
Industrial and domestic wiring, is always well insulated.
The wires are covered, with a insulating material, like plastic.
The external casing of the appliances that we use, are insulated from the wiring inside.
If due to a wiring fault, the casing comes into contact, with electricity,
it will conduct electricity.
If we touch this appliance, we will get a electric shock, which can be dangerous.
High power electrical appliances, use a 3 pin socket.
One pin, is the positive or “live” terminal.
One pin, is the neutral terminal.
When the appliance is plugged in, electricity flows from the live terminal,
through the appliance, to the neutral terminal.
This is the normal working pattern, of the appliance.
Electricity always flows through the easiest path available.
The ground can be considered, as the most electrically neutral place.
If we provide an easy path, for the electricity to flow to the ground,
its first choice will be to do so.
We take advantage of this fact, to provide one level of safety.
One wire in electrical wiring, is directly connected, to the ground.
This is usually called as the grounding, or earthing.
The third pin, of the electrical socket, is connected to the ground or earthing.
In case of electrical leakage, the third pin, provides a easy path,
for electricity to flow, to the ground.
This provides one level of safety, for us, from electrical shocks.
The electric fuse, is another way to protect us.
If the water heater, in our bath room, has a wiring fault,
it causes electricity to leak, to the casing.
If we touch the casing, we offer an alternative electrical path, for the electricity.
Electricity, flows through us, to the ground.
When such a thing happens, the magnitude of current flow increases.
A fuse is so designed, that when a current exceeds a certain capacity,
the fuse wire, will melt.
The circuit will be broken.
Miniature circuit breakers, or MCBs, also function like a fuse.
An MCB will disconnect or break the circuit,
when the current exceeds a certain value.
A 5 amps MCB, will break the circuit, if the current exceeds, 5 amperes.
A 15 amps MCB, will break the circuit, if the current exceeds, 15 amperes.
Fuses and MCBs, offers us one more level of protection.
Electricity is the most useful form of energy,
but it has to be handled with care.