Transcript 16.2 Forms of Energy

Forms and Uses of
Energy
16.1 What is Energy?
• Energy is the ability to do work.
• Living things need energy for the
processes that keep them alive.
• Non-living systems also need energy to
function.
o For example, cars and aeroplanes need fuel
to provide them with energy to move.
16.2 Forms of Energy
• Potential Energy
o Potential energy is stored energy due to a
body’s position or condition.
16.2 Forms of Energy
• Examples of potential energy:
o Chemical potential energy
• Energy stored in fuels such as petrol and food that
can be released through chemical reactions.
16.2 Forms of Energy
• Examples of potential energy:
o Gravitational potential energy
• Energy that an object has because of its position
or location.
• When the object is in a higher position with respect
to the ground, it has more gravitational potential
energy than in a lower position.
16.2 Forms of Energy
• Examples of potential energy:
o Elastic potential energy
• Energy that an object has when it is stretched or
compressed.
16.2 Forms of Energy
• Kinetic Energy
o Kinetic energy is the energy that a body has
due to its motion.
• All moving objects have kinetic energy.
• Examples: a bird flying in the sky, a girl walking
down the street and a car speeding down the road.
16.2 Forms of Energy
• Heat
o Heat is the energy that flows from a
region of higher temperature to one of
lower temperature.
• Heat flows from things that are hot.
• The Sun is an important source of heat
energy during the day.
• Heat is used in homes for cooking, heating
water, ironing clothes.
• In factories, heat is needed for processes
like melting metals, creating steam to turn
turbines and making chemicals react.
16.2 Forms of Energy
• Light
o Light is the energy that enables us to see.
• Things that are luminous can give out light energy.
• The Sun is an important source of light energy during
the day.
• Without light, the world would be completely dark,
and we would not be able to see things around us.
16.2 Forms of Energy
• Sound
o Sound is the energy produced when objects
vibrate.
• Sound allows us to communicate and enjoy music.
• Sound is also used as a warning.
– For example, when a fire breaks out, the fire alarm goes
off and alerts everyone to get to safety.
16.2 Forms of Energy
• Electricity
o Electricity or electrical energy is the energy
that results from the flow of charged particles.
• Electricity is a useful form of energy that can be
transformed into many other forms of energy.
• Almost all electrical appliances or equipment in
homes and offices need electricity to work.
16.3 Energy Transformations
• Photosynthesis in plants
o Light energy  Chemical potential energy
16.3 Energy Transformations
• An archer releasing his bow
o Elastic potential energy  Kinetic energy
16.3 Energy Transformations
• A moving car
o Chemical potential energy  Kinetic energy +
Sound energy + Light energy + Heat energy
16.3 Energy Transformations
• Generation of electricity
o Electricity is a useful form of energy.
o Electrical generators are used to convert
kinetic energy to electricity.
o Power stations produce large amounts of
electricity needed in homes, schools and
offices.
o In a power station, a series of energy changes
occur before electricity is produced.
16.3 Energy Transformations
• In a power station
1. A fuel such as coal, oil or
natural gas is burnt and heat
is produced to boil the water
in the boiler.
Chemical potential energy of
fuel  Heat energy of water
3. The turbines are connected to a
2. The heat energy turns water into
generator, which converts the kinetic
steam at high pressure, which goes
energy of the turbine blades into
through the boiler and turns the
electricity.
turbines.
Kinetic energy of turbines  Electricity
Potential and kinetic energy of
steam  Kinetic energy of turbines
steam line
turbine
generator
coal supply
switchyard
boiler
condenser
cooling water
16.3 Energy Transformations
• Generation of electricity
o In a nuclear power station, nuclear reactions occur by
bombarding radioactive elements with neutrons.
o This creates large amounts of heat to boil the water into
steam to turn turbines.
o Nuclear energy in radioactive elements  Heat 
Kinetic energy of steam  Kinetic energy of turbines 
Electricity
16.4 Law of Conservation of
Energy
• Energy transformations in a swing
When the swing is at its
highest point, A, it only has
gravitational potential
energy. When the swing is
midway between A and B,
some of the gravitational
potential energy is
converted to kinetic energy.
When the swing is at its
lowest point, B, all the
gravitational potential
energy has been
converted to kinetic
energy.
A
C
B
16.4 Law of Conservation of
Energy
• Energy transformations in a swing
o In theory, the child would be able to swing to
and fro for an unlimited period of time.
o However, the swing will eventually stop moving if no one
gives it a push every now and then. What happened to
the energy?
o The law of conservation of energy states that energy
can change from one form to another, but it cannot be
created or destroyed.
o When energy is not lost, we say it is conserved. The
swing stops moving as the energy was converted to
other forms of energy such as heat and sound energy
due to friction between the swing and surrounding air.
16.4 Law of Conservation
of Energy
• Energy transformations
in a ball falling on the
floor
o Let the total energy
possessed by the ball be
E.
o According to the
conservation of energy,
the total amount of
energy, E, does not
change.
At position B, the ball is
falling.
It gains
kinetic
At position
A, the
ball
energy,
KEB, while
has potential
energy
losing
some
potential
PEA. This
is equal
to E.
energy. The potential
PEAat=position
E
energy left
B
is PEB .
At
the ballC,
hits
the
AtD,position
just
KE
B + PEB = PEA = E
floor
andthe
becomes
before
ball hits the
compressed.
A sound is
floor, only kinetic
heard
andKE
heat
energy
left.
C is is
produced due to friction.
KEC = PEC + KEC = PEA
Elastic
= E potential energy
of ball + heat + sound =
E
A
B
C
D
16.4 Law of Conservation
of Energy
• Energy transformations in
a ball falling on the floor
o Then ball is unable to reach
its original height of position
A when it bounces back up.
o This is because some of the
energy, E, is lost as sound
and heat when it hits the
floor.
o With less energy, the ball
cannot regain its original
height.
A
B
C
D
16.5 Conserving Energy
• It is important to conserve
energy because most of
the energy we use comes
from non-renewable
resources.
• Non-renewable resources
include crude oil and coal.
These sources of energy
are limited and will run
Coal
Extracting,
power plants
processing
produce
and
more
burning
pollution
crude than
oil cause
oil power
large plants.
amounts
Butofcoal
out one day.
is more
pollution,
commonly
which destroy
used in developing
the
countries
environment.
as it is cheaper than oil.
Renewable sources of energy
• Renewable sources of energy are
sources of energy that can be sustained or
renewed indefinitely, due to unlimited
supplies or because of new growth.
Renewable sources of energy
• Solar energy
o Solar energy is used in solar furnaces for
smelting iron.
o Solar energy is also used to generate steam
in power station. This steam is used to turn
turbines of a generator to produce electricity.
Renewable sources of energy
• Wind energy
o A wind farm is a
collection of wind
turbines used to
generate electricity.
o The wind turbines
use the kinetic
energy of the wind
to generate
electrical energy.
Renewable sources of energy
• Wave energy
o Wave farms use the
kinetic energy of
waves to generate
electricity.
o The up-and-down
movement of the
wave will shift gears to
turn turbines to
generate electricity.
Renewable sources of energy
• Biomass
o Biomass refers to plant and animal material
from which we can:
• extract oil (oil palm, jatropha, jojoba)
• ferment into gas (water hyacinth, manure)
• burn (dried plant material, wood, charcoal)
Renewable sources of energy
• Conserving energy in Singapore
o Singapore uses natural gas for its power
stations but has started using solar energy,
wind energy and biomass.
o Since Singapore does not have many natural
resources, we are dependent on other
countries for our fuel needs.
o Hence, it is important for us to be aware of
conserving energy.
Renewable sources of energy
• Conserving energy in Singapore
o We should use energy more efficiently and
avoid wasting electricity.
o For example, you should turn off electrical
appliances that are not in use.
Miscellaneous
• http://www.eia.doe.gov/kids/energyfacts/science/f
ormsofenergy.html
• http://en.wikipedia.org/wiki/Energy_transformatio
n
• http://www.glenbrook.k12.il.us/gbssci/phys/mmedi
a/energy/ce.html
• http://fi.edu/guide/hughes/energyconservation.ht
ml
• http://www.reupower.com/energysvc/53ways.html
• http://www.eia.doe.gov/kids/energyfacts/sources/r
enewable/renewable.html