1. By Tushar Gupta
Class 10
RESONANCE
Topic: Energy

2. What is energy ?
• Energy is the capacity of a body for
doing work.
• Energy stored in a body or a system
is equivalent to total work done by
the body till whole whole of the
energy has been completely
exhausted.

3. • Most of our energy requirement is
fulfilled from the fuels and
electricity.
• Energy can be converted from one
form to another.

4. Energy is everywhere

5. History of energy use
• Date back several thousand years ago.
Sun is probably the first source of
energy known to mankind.
• Animals learn "energy" and its "power"
when getting warmth under sun and
when facing the danger of a forest fire
due to lightning.

6. Forms of energy
In everyday life, energy
exists in these eight
forms:
• Mechanical (kinetic and
potential)
• Chemical
• Nuclear
• Heat
• Light
• Electrical
• Sound

8. More details about the
eight forms of energy
• Mechanical energy is
• The energy of motion (kinetic) and the
energy of position (potential)
• Elastic potential energy is stored in a
stretched spring or a bowstring
• When an object is lifted above the
ground, it has gravitational potential
energy

9. • Chemical energy
• The energy that bonds
molecules together.
• Nuclear energy
• Energy released, when
some changes take place in
the nucleus of an atom of a
substance.

10. • Thermal (heat) energy
• Energy of moving and vibrating
molecules
• A specific kind of kinetic
energy.
• Light energy
• Hot objects like a filament lamp
or a gas mantle give off light
• Light is a form of
electromagnetic radiation.

11. • Electrical energy
• Energy of moving electrons
• Electrical appliances use it
to operate
• Sound energy
• Vibrating objects produce
sound
• A form of energy detected
by the ear. Music and noise
are sound.

12. How do we use energy?
To human, its main function can be
grouped into five main categories:
• Energy allows us to see
• Energy give us warmth
• Energy produces growth
• Energy produces motion
• Energy powers technology

13. Energy Sources
Classified as non-renewable and renewable
sources .
Non-renewable Renewable
(1) Petroleum (Oil) (1) Hydropower
(2) Natural Gas (2) Geothermal
(3) Coal (3) Solar
(4) Propane (4) Wind
(5) Uranium (5) Biomass

15. Non-renewable Sources of energy
• Non-renewable sources require millions of years
of natural processes to be produced and cannot
be replenished.
• Coal , petroleum and natural gas and propane are
also known as fossil fuels

16. Fossil fuels as source of electricity
and mains of heating and
transportation

17. Distribution of fossil
fuel use in the world
natural gas
25% petroleum 38%
coal 21%
others 16%

18. Renewable Sources of
energy
Five renewable sources used most often
include hydropower, solar, wind, geothermal,
and biomass can be replenished in a short
period of time

19. Solar energy
• Sunlight is the most abundant
energy source on the earth
• On average, the earth's surface
receives about 1.2 x 1017 W of
solar power
• Most of the other renewable
energy also depend on the sun as
the primary source

20. Advantages of
Renewable Energy at
Macro and Micro Level

21. Composition of solar
energy (Sunlight)
Composition of sunlight
Ultra- violet rays Visible light Infra red rays

22. Sun is never –ending energy supply source

23. Wind energy
• Wind contains kinetic energy
• The higher the wind speed ,the
higher the kinetic energy
• Kinetic energy of the wind→
rotor( blades with an
aerodynamic profile) →
transmits the rotational
motion via a gear set to the
generator → power

24. Geothermal energy
• Natural heat
extracted from
the earth's crust
• In form of heat,
which originates
deep in the earth's
molten interior
• Responsible for
volcanoes and
earthquakes

25. Biomass energy
• Utilization of organic waste
to produce energy
• Chemical energy stored in
plants and animals or in the
animal waste is called bio-
energy
• Burning of the biomass will
release the energy in the
form of heat

26. Hydropower
• Capture the kinetic
energy of falling water to
generate electricity
• Flowing or falling water
rotates turbines and
generators where kinetic
energy is converted to
mechanical → electrical
energy

27. What is a good source of
energy?
We could say that a good source of
energy would be one
• Which would do a large amount of
work per unit volume or mass,
• Be easily accessible,

28. • Be easy to store and transport, and
• Perhaps most importantly, be
economical

29. How much energy do we
use?
• According to the Key World Energy Statistics
(2002 Edition) from the International Energy
Agency (IEA), the world consumption
breakdown of primary energy in 2000 is as
follows:

30. Energy Conversions
• All forms of energy can be converted
into other forms.
– The sun’s energy through solar cells can
be converted directly into electricity.
– Green plants convert the sun’s energy
(electromagnetic) into starches and
sugars (chemical energy).

31. – In an electric motor,
electromagnetic energy is
converted to mechanical energy.
– In a battery, chemical energy is
converted into electromagnetic
energy.
– The mechanical energy of a
waterfall is converted to
electrical energy in a generator.

32. Chemical  Heat
Mechanical
• In an automobile engine, fuel is
burned to convert chemical energy
into heat energy. The heat energy is
then changed into mechanical energy.

33. Do you know???
• Since the 1980s the
Hong Kong Observatory
has employed solar cells
to power some automatic
weather stations in many
places of Hong Kong. Up
to now, there are over
20 stations equipped
with solar cells.

34. Energy and Environment
Pollutants
• Burning of fossil
fuels produce air
pollution. The
followings are a
brief description
of the air
pollutants:

35. Diagram showing pollution
linked with burning fossil fuels
Volatile organic
compounds

36. Carbon dioxide
• Carbon dioxide is released into the
atmosphere as a result of burning fossil
fuels such as coal, oil and natural gas.
• Increases in carbon dioxide concentrations
results in global warming due to greenhouse
effect.
• It is predicted that the temperature of the
world would rise by 1.5°C in 50 years. This
in effect alters precipitation patterns and
raises sea levels by about one metre.

37. Nitrogen oxides
• Nitrogen oxides (NOx) are released by
burning fossil fuels at electric power
plants and in automobiles,
• Nitrogen oxides are an important
precursor to ozone and acid rain. NOx,
when mixed with other chemicals in air
under the action of sunlight, generates
photochemical smog and reduced
visibility

38. Sulphur dioxide
• Sulphur dioxide (SO2) comes from the
combustion of fuel containing sulphur,
mostly coal and oil
• NOx and SO2 produces acid rain, which
is the main cause of acidification of
lakes, accelerated corrosion of
buildings and monuments.

39. Mercury
• Mercury is a heavy metal that is
discharged into the air and
accumulates in our lakes, streams and
ultimately inside our bodies
• The largest sources of mercury in
the environment are coal-fired power
plants, medical waste and municipal
waste incinerators

40. Ozone
• Ozone is formed under a complex
chain of chemical reactions in the
presence of sunlight and high
temperatures involving a host of
precursors
• Major ones are oxygen, nitrogen
oxides (NOx) and reactive volatile
organic compounds (VOC)
• Common VOC source include paints

41. Energy crisis
• Power plant, industries, buildings and
motor vehicles rely heavily on fossil
fuels, such as coal, oil and natural gas
• Unfortunately, human activities have
resulted in the consumption of these
scarce natural resources

42. • Fossil fuels are also unevenly
distributed around the world.
Although only one-quarter of the
world's population lives in
developed countries, the energy
consumption accounts for three-
quarters of total consumption in
the world
• Less developed countries often
have to promote economic growth
and to cope with high population
growth

43. • Global demand for oil will grow by an
estimated 50% during the next several
decades, while both coal and natural gas
consumption are expected to double

44. U.S. energy consumption
by source

45. Effects on Hong Kong
• No indigenous energy resources in
Hong Kong, we have to rely totally on
imported fuels, and we know that fossil
fuels are already exhausting.

46. Conserve energy
• Since fossil fuels are a nonrenewable
source of energy, it is important that
we conserve energy
• We can conserve energy by turning off
lights when they are not being used,
walk instead of drive if we are going
short distances and wear layers of
clothes to keep warm.

47. How to save energy in
daily lives?
• Minimize energy use
• Use energy efficiently
• Minimize energy loss

48. Minimize energy use
• Use ventilation or fans
where possible
• Relocate where seats under
direct sunlight that require
strong air-conditioner for
comfort

49. • Organize "Dress Casual Day" on a weekly
basis where air-conditioner is adjusted to
a slightly higher temperature
• Turn off some or all air-conditioners 15
minutes before leaving the room

50. Use energy efficiently
• Preferred air-conditioner temperature
set-point is 25.5 ºC when the outdoor air
temperature is above 25.5 ºC for
acceptable comfort conditions of least
energy consumption

51. • Clean air-conditioner and dust filter
regularly
• Establish a maintenance program to ensure
air-conditioner is operating efficiently

52. Minimize energy Loss
• Keep windows and doors closed to minimize
air infiltration when air-conditioner is
running
• Lower window blinds or curtains to reduce
direct sunlight during summer time

53. • Turn off some lighting when the occupancy
is low (e.g. on Saturdays)
• Turn off lighting in public areas (e.g.
pantries, lavatories, circulation space etc.)
during lunch and after office hours

54. What have we learnt?
• Energy does work.
• Energy is never ‘used up’ it is simply
converted from one form to another.
• Fuels and food are sources of energy.
• There are 3 main classes of fuel which
can be used to generate electricity:
Fossil fuels, renewable fuels and
nuclear fuels.

55. • Fossil fuels such as gas, coal and oil
and renewable fuels such as wood are
burnt and heat is generated.
• This heat is used to boil water and the
steam that is created is used to turn
large propellers called turbines.
• These turbines then turn electrical
generators.
• There are other sources of energy
such as: Solar power, wind power,
hydroelectric power and wave power.

56. Conclusion
• To make sure we have plenty of
energy in the future, it's up to all of
us to use energy wisely
• We must all conserve energy and use
it efficiently. It's also up to those
who will create the new energy
technologies in the future

57. THE FUTURE IS IN
YOUR HANDS!