Transcript New Energy transfer

Energy basics
• ‘Work’ is done when a force acts
on an object to cause it to
move, change shape, displace,
or do something physical.
• Thermal energy is what we call
energy that comes from the
temperature of matter. The hotter
the substance, the more its
molecules vibrate, and the
therefore the higher its thermal
energy.
The amount of thermal energy in
an object is measured in Joules
(J)
• For example, a cup of hot tea
has thermal energy in the form
of kinetic energy from its
vibrating particles. When you
pour some milk into your hot
tea, some of this energy is
transferred from the hot tea to
the particles in the cold milk.
What happens next? The cup of
tea is cooler because it lost
thermal energy to the milk.
Temperature
and Heat
We cannot discuss
thermal energy without
touching on
Temperature.Temperatu
re and heat are NOT
THE SAME.
Temperature
How hot or cold it is.
Measured in degrees Celsius.
Heat/Thermal
The amount of thermal energy,
measured in joules or J.
A cup of hot tea
has heat energy in
the form of kinetic
energy from its
particles.
A swimming pool at 30°C is
at a lower temperature
than a cup of tea at 80°C.
BUT
the swimming
pool contains
more water, so
it stores more
thermal energy
or heat.
The small beaker of
water boils first
The large
beaker
contains
more water
and needs
more
thermal
energy or
heat to
reach 100°C.
Chemical Energy is energy
stored in the bonds of chemical
compounds (atoms and
molecules). It is released in a
chemical reaction. Chemical
energy can be stored and then
transferred to the surroundings
as thermal energy, sound
energy and kinetic energy.
Sound is produced when a force
causes an object or substance
to vibrate (eardrum) — the
energy is transferred through
the substance in a wave.
Kinetic energy (movement
Electrical energy is energy that's
stored in charged particles
within an electric field. Electric
fields are simply areas
surrounding a charged particle.
Energy
transfer
Energy transfer
• Example: The battery transfers
stored chemical energy as
electrical energy. The electrical
energy is transferred to the
surroundings by the lamp as
light energy and thermal energy
(heat energy).
The Law of
Conservation of Energy
Energy is always conserved, it
is never "lost" or "wasted“.
Energy is not created or
destroyed!
Two Types of
Energy:
1) Kinetic Energy
2) Potential Energy
Potential Energy
•Potential Energy is
stored energy.
•An object with potential
energy has the ability to
move or change.
•Potential energy
depends on an object’s
position or condition.
• Gravitational Potential energy is
only stored in the height of the
object. Any time that a heavy
object is kept high up, a force or
power is likely to be holding it
up there. This is the reason why
it stays up and does not fall. It
is important to note that the
heavier the object, the more its
potential energy.
Examples:
Kinetic Energy
• Kinetic Energy is
the energy of
movement.
• It depends on the
mass and speed of
a moving object.
Examples:
Potential or
Kinetic?
Potential or
Kinetic?
Potential or
Kinetic?
Potential or
Kinetic?
Potential or
Kinetic?
Potential or
Kinetic?
Heat
A Form of Energy
Molecules and Motion
• The motion of
molecules produces
thermal energy/heat.
• The more motion, the
more heat is generated.
Heat Transfer
• Heat is the flow of
thermal energy from a
warmer object to a
colder one.
Forms of heat transfer
• Three forms of heat
transfer:
• Conduction
• Convection
• Radiation
Conduction
• Conduction involves the
transfer of heat through
direct contact
• Molecules transfer
energy as they collide
with adjacent molecules.
Conductors & Insulators
• Conductors allow energy to
flow easily. Ex. metals &
glass – think of cookware
• Insulators are poor
conductors. Ex. wood,
plastic, fabric – think of the
handles on cookware or an
oven mitt.
Convection
• This is the transfer of
energy in liquids and
gases as molecules move
in currents.
• Warmer molecules rise
and the cooler ones sink.
Radiation
• Heat is transferred through
empty space. Ex.
electromagnetic waves and
visible light
• Energy from the sun
radiates to Earth. *Other hot
objects can radiate as well.
Questions
• What are the three
types of heat transfer?
• How is conduction
different from
radiation?
Answer: What type of
heat transfer is
involved?
•
Heating a room with a
fireplace
Convection
• Egg cooking in a frying pan
Conduction
• Roof of a house becoming
hot
Radiation
Answer: What type of
heat transfer?
1. Warm air mass
bringing a change in
the weather
2. Wire getting hot from
an electric appliance
Properties of Light
• Reflection- when an object or
wave bounces back off a
surface
Electromagnetic
Waves waves without a
• Transverse
medium!
• (They can travel through empty
space)
• Electromagnetic Spectrum—name for
the range of electromagnetic waves
when placed in order of increasing
frequency
RADIO
WAVES
INFRARED
RAYS
MICROWAVES
ULTRAVIOLET
RAYS
VISIBLE LIGHT
GAMMA
RAYS
X-RAYS
RADIO WAVES
• Have the
longest
wavelengths
and lowest
frequencies
of all the
electromagne
tic waves.
MICROWAVES
• Have the
shortest
wavelengths
and the
highest
frequency of
the radio
waves.
INFRARED RAYS
• Infrared=
below red
• Shorter
wavelength
and higher
frequency
than
microwaves.
VISIBLE LIGHT
• Shorter wavelength
and higher frequency
than infrared rays.
• Electromagnetic
waves we can see.
• Longest
wavelength= red
light
• Shortest
wavelength= violet
(purple) light
ULTRAVIOLET RAYS
• Shorter
wavelength
and higher
frequency
than visible
light
• Carry more
energy than
visible light
X- RAYS
• Shorter
wavelength
and higher
frequency
than UV-rays
• Carry a great
amount of
energy
• Can
penetrate
most matter.
GAMMA RAYS
• Shorter
wavelength and
higher frequency
than X-rays
• Carry the greatest
amount of energy
and penetrate the
most.