Friday 9 November 2012
HEAT TRANSFER
Energy Likes to Move
If there is a temperature difference in a system, heat will naturally move from high to low temperatures. The place you find the higher temperature is the heat source. The area where the temperature is lower is the heat sink.Ever Hear of Convection Ovens?
Convection is the way heat is transferred from one area to another when there is a "bulk movement of matter." It is the movement of huge amounts of material, taking the heat from one area and placing it in another. Warm air rises and cold air replaces it. The heat has moved. It is the transfer of heat by motion of objects. Convection occurs when an area of hot water rises to the top of a pot and gives off energy. Another example is warm air in the atmosphere rising and giving off energy. They are all examples of convection. The thing to remember is that objects change position.Radiating Energy
When the transfer of energy happens by radiation, there is no conductive medium (such as in space). That lack of medium means there is no matter there for the heat to pass through. Radiation is the energy carried by electromagnetic waves (light).Conducting Energy and Heat
Conduction is a situation where the heat source and heat sink are connected by matter. As we discussed before, the heat flows from the source down the temperature gradient to the sink. It is different from convection because there is no movement of large amounts of matter, and the transfers are through collisions. The source and the sink are connected.
If you touch an ice cream cone, the ice cream heats up because you are a warmer body. If you lie on a hot sidewalk, the energy moves directly to your body by conduction.
http://www.physics4kids.com/files/thermo_transfer.html
MECHANICAL ENERGY
Mechanical energy is the energy which is possessed by an object due to its motion or its stored energy of position. Mechanical energy can be either kinetic energy (energy of motion) or potential energy (stored energy of position). Objects have mechanical energy if they are in motion and/or if they are at some position relative to a zero potential energy position (for example, a brick held at a vertical position above the ground or zero height position).
A moving car possesses mechanical energy due to its motion (kinetic energy). A moving baseball possesses mechanical energy due to both its high speed (kinetic energy) and its vertical position above the ground (gravitational potential energy). A World Civilization book at rest on the top shelf of a locker possesses mechanical energy due to its vertical position above the ground (gravitational potential energy). A barbell lifted high above a weightlifter's head possesses mechanical energy due to its vertical position above the ground (gravitational potential energy). A drawn bow possesses mechanical energy due to its stretched position (elastic potential energy).
An object which possesses mechanical energy is able to do work. In fact, mechanical energy is often defined as the ability to do work. Any object which possesses mechanical energy - whether it be in the form of potential energy or kinetic energy - is able to do work. That is, its mechanical energy enables that object to apply a force to another object in order to cause it to be displaced.
Numerous examples can be given of how an object with mechanical energy can harness that energy in order to apply a force to cause another object to be displaced. A classic example involves the massive wrecking ball of a demolition machine. The wrecking ball is a massive object which is swung backwards to a high position and allowed to swing forward into building structure or other object in order to demolish it. Upon hitting the structure, the wrecking ball applies a force to it in order to cause the wall of the structure to be displaced.
http://www.kids.esdb.bg/mechanical_principles.html
MORE SOUND!
. Sound is energy that is made by vibrations. When any object vibrates it causes movement in the air.
The air particles then bumps into each other and then bump into others. This continued bumping cause
The air particles then bumps into each other and then bump into others. This continued bumping cause
a sound wave.
2. If the human ear is within the range of the vibrations, a sound can be heard.
3. When the vibrations are fast, the sound is high. When the vibrations are slow, the sound is low.
4. Sound waves are also called pressure waves because they move the particles they are passing through.
5. The ear is not the only detector people and animals have. Sound waves can even be felt by different
parts of the body. Sometimes you can feel the vibrations thunder makes while you are actually hearing it.
6. Stringed instruments are played when fingers or a bar are pressed down on the strings. This pressure
changes the strings' length, causing them to vibrate at different frequencies and make different sounds.
Shortening a string makes it sound higher, while lengthening a string can produce a lower sound.
Strings also produce different sounds depending on how thick they are.
7. In wind instruments, there is a reed (a thin piece of wood inside the mouthpiece, that vibrates
when air travels over it. The keys produce different size openings in the instrument. The air columns
inside the instrument are then made shorter or longer which produces different sounds.
8. Sound waves can bend around corners and obstacles.
9. The human ear that is attached to the side of the head acts as a funnel to catch sounds. The inner ears,
eardrums and tiny bones inside the ear called the hammer, anvil and stirrup all begin to vibrate. Sound
vibrations then move through an oval opening called the cochlea. In the cochlea--a snail shell-like,
fluid-filled chamber--the sound waves stimulate tiny hairs that are connected to the auditory nerve.
The auditory nerve receives signals from the nerve cells and transmits them to the auditory center in the brain.
10. The brain receives these messages from the auditory nerve. The messages comes in fast and furious,
in a jumble of confusion, but the brain has the ability to sort them into an organized pattern.
This way we can understand the sounds we hear as music or human speech.
http://www.kidskonnect.com/subjectindex/15-educational/science/88-sound.html
Facts about Sound
Sound Facts
Learn some interesting facts about sound that you might not have known. Understand how sound waves come from vibrations and how your ears give you the ability to hear them. Find out what the speed of sound is, how sound relates to music, the meaning of acoustics and much more.
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Sunday 4 November 2012
Sunday 28 October 2012
LIGHT ENERGY
Background Information & Activities
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| © 1999-2012 BrainPOP. All rights reserved. |
What do many living things need to survive? Most plants and animals rely on food, water, shelter, and light in some way. In this movie, children will learn about an energy that is all around us and helps us see the world: light! But what is light? Remind children that light is a type of energy, like heat or sound. The Sun, stars, lightning, and fire are all natural sources of light. Living things need light to survive, including plants, animals, and people. People use electricity to light their homes and some use solar power, which converts sunlight into electricity. Light is made up of tiny particles that travel in waves. Light travels until it hits an object and is either absorbed or reflected. We can see because light is reflected from an object to our eyes. Light can pass through transparent, or clear objects, but not through opaque ones. Objects that block light can cast shadows. Colored glass objects block some light but also allow some light to pass through, while translucent objects, like frosted glass or wax paper, diffuse light and prevent clear vision of whatever is on the other side.
Many living things rely on light to survive. Plants convert sunlight into food via photosynthesis to grow and change. Cold-blooded animals such as reptiles, amphibians, and insects rely on light to warm their bodies. People need light to grow crops, but they also need light to see. People use electricity to power their light bulbs and light their homes. Many buildings and electronics use solar power, a renewable energy resource which uses special devices that convert sunlight into electricity.
Remind children that light moves very, very quickly—at 186,282 miles per second, or 299,792,458 meters per second. Light rays travel in one direction until they hit an object. Light reflects, or bounces off the object and into our eyes so we can see it. The object also absorbs, or takes in, some light. Objects that are shiny, such as metal pots and mirrors, reflect light better than dull objects such as dark sweaters or fuzzy toys, which absorb more light. Smooth, flat mirrors reflect light in roughly the same angle the light hits them so we can see reflections. When light hits curvy mirrors, it bounces off in many different directions and back to our eye. We see our reflections, but they are distorted.
Light can easily pass through some objects, such as clear plastic or glass. These objects are transparent and we can see through them. Light cannot pass through opaque objects, such as wood blocks. Objects that block light can cast shadows. Show children that when an object blocks light, light cannot pass through to the other side. You see a dark spot that’s shaped like the object—a shadow. This is how we know that light travels in straight lines; if it curved, it would bend around opaque objects and shadows would not be made. Some objects block some light but also allow some light to pass through. Sunglasses and stained glass block some light. Translucent objects diffuse light in many different directions. It is difficult to see through translucent objects such as sheer fabric, wax paper, frosted glass, or tissue paper.
When light passes through objects, it refracts, or changes direction. Place a spoon in a clear glass of water. What happens? The spoon looks like it’s broken. When light travels through water or glass, it slows down and changes directions or “bends.” Then as it passes through to air, it speeds up again. This changes the way we see the object. Binoculars, telescopes, microscopes, and magnifying glasses all refract light in different ways so we can see things in closer detail.
Light is a complex and fascinating subject that children can explore all on their own.
SOUND ENERGY
Sound energy
Sound is the movement of energy through substances in longitudinal (compression/rarefaction) waves.
Sound is produced when a force causes an object or substance to vibrate — the energy is transferred through the substance in a wave. Typically, the energy in sound is far less than other forms of energy.
Let's see this illustration.
A vibrating drum in a disco transfers energy to the room as sound. Kinetic energy from the moving air molecules transfers the sound energy to the dancers eardrums. Notice that Kinetic (movement) energy in the sticks is being transferred into sound energy.
Sound vibrations create sound waves which move through mediums such as
air and water before reaching our ears.
http://www.eschooltoday.com/energy/kinds-of-energy/what-is-sound-energy.html
Sound is the movement of energy through substances in longitudinal (compression/rarefaction) waves.
Sound is produced when a force causes an object or substance to vibrate — the energy is transferred through the substance in a wave. Typically, the energy in sound is far less than other forms of energy.
Let's see this illustration.
A vibrating drum in a disco transfers energy to the room as sound. Kinetic energy from the moving air molecules transfers the sound energy to the dancers eardrums. Notice that Kinetic (movement) energy in the sticks is being transferred into sound energy.
Sound vibrations create sound waves which move through mediums such as
air and water before reaching our ears.
http://www.eschooltoday.com/energy/kinds-of-energy/what-is-sound-energy.html
THERMAL ENERGY
Heat (Thermal energy)
Thermal energy is what we call energy that comes from heat. For example, a cup of hot tea has thermal energy in the form of kinetic energy from its particles. When you pour some milk into your tea, some of this energy is transferred to the particles in cold milk. What happens next? The cup of tea is cooler because it lost thermal energy to the milk.
We cannot discuss Thermal Energy without touching on Temperature.
Temperature
The temperature of an object is to do with how hot or cold it is, measured in degrees Celsius (°C). A thermometer is used to measure the temperature of an object.
Let's look at two examples to see the difference between
heat and temperature.
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 than the cup of tea.
To boil water we must increase its temperature to 100°C. It takes longer to boil a large beaker of water than a small beaker because the large beaker contains more water and needs more thermal energy to reach 100°C.
Thermal energy is what we call energy that comes from heat. For example, a cup of hot tea has thermal energy in the form of kinetic energy from its particles. When you pour some milk into your tea, some of this energy is transferred to the particles in cold milk. What happens next? The cup of tea is cooler because it lost thermal energy to the milk.
We cannot discuss Thermal Energy without touching on Temperature.
Temperature
The temperature of an object is to do with how hot or cold it is, measured in degrees Celsius (°C). A thermometer is used to measure the temperature of an object.
Let's look at two examples to see the difference between
heat and temperature.
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 than the cup of tea.To boil water we must increase its temperature to 100°C. It takes longer to boil a large beaker of water than a small beaker because the large beaker contains more water and needs more thermal energy to reach 100°C.
Now let's see three very important forms of heat energy transfer.
These are Conduction, Convection and Radiation
These are Conduction, Convection and Radiation
ENERGY PIONEERS
USES OF ENERGY
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