How Does a Lightbulb Work?

A light bulb is made from a very thin piece of glass. The glass is heated up and blown into a shape of a bulb. Once cooled, the inside of the bulb is coated with a material that diffuses the light. The filament of a light bulb is made of tungsten. Tungsten is a metal like element that burns in the presence of oxygen. The tungsten wire that the filament is made from is very thin, on the order of 0.0017 inches thick! The filament is made of coiling the tungsten wire around itself, forming a double coil. The ends of the coil are then attached to power leads that are inside the glass base of the bulb. The glass top and bottom are then melted together, the bulb is sealed, and the oxygen is removed from the bulb. Various gases can then be introduced into the bulb. A metal base is added and the bulb is ready to use.

In a normal light bulb an electric current travels through a coiled tungsten wire. Current is carried in a wire by bumping electrons off of the atoms or molecules that make up the wire, like marbles. One electron is bumped which bumps another electron. Electrons do not collect within the wire, but rather one electron is bumped and replaced in the atom by the one that bumped it. This bumping creates energy. The energy is released as heat in the filament and can heat the filament to up to 2500 degrees Celsius! At 2500 degrees Celsius the light bulb emits about 12% of its energy as visible light. Energy is also given off from the bulb as invisible infrared light or heat.

Evidence exists that Thomas Edison was not actually the inventor of the light bulb. In 1878 British inventor Joseph Swan patented the carbon filament light bulb. That following year Edison patented the same carbon filament bulb. As a result of the law suit Swan flied against Edison, the Edison and Swan Electric Company was formed. In 1882 Swan sold his patent to Brush Electric Company. Edison owned Brush, later General Electric, and got the credit for the patents. The light bulb developed by Swan and Edison is based on the same principles as the ones we currently use today. Improvements in the make up of the filaments have been made to lengthen the life of the bulb.

In neon lights, similar concepts are used. Different gases and coatings can be added to the glass to induce different colors.

How Do Sun-Powered Homes Work?

Most existing buildings, including your home, are powered through an electrical grid.This grid connects all the homes in your neighborhood and all the buildings downtown through wires. At a power plant the wires all come together. A power plant generates the electricity that you use to light, heat, and cool your home. Power also allows you to turn on your hair dryer, your computer, and your microwave.The power that is produced at most of these power plants comes from fossil fuels.

There are three forms of fossil fuels: coal, oil, and natural gas. All three were formed several hundred million years ago, before the time of the dinosaurs. This time period is called the Carboniferous Period and occurred about 360 million years ago. The planet was covered with swamps, trees, and large leafy plants. As the plants died, they sunk to the bottom of the swamps. Over many, many years, these plants were covered with sand, rocks, and other minerals. Eventually, all the water within the plants was squeezed out. The remaining material became coal, oil, or natural gas.

Mining companies take these fossil fuels out of the earth and use them to generate electricity. In order to produce energy, power plants burn fossil fuels. These fuels give us the energy to run our cars and power our homes. However, fossil fuels take millions of years to make. Right now, we are using fossil fuels that were made over 300 million years ago. If we don't conserve the fossil fuels that we have, we may run out!

HAVE NO FEAR! There is an alternative to using fossil fuels. Any guesses?

The sun and the wind! Scientists are discovering more ways to use renewable energy sources such as the sun and wind. Renewable means that unlike fossil fuels, which are limited in energy, these sources will not run out. Another bonus to using renewable resources is that they don't pollute the environment the way fossil fuels do. When fossil fuels are burned, they release gases into the air. These gases can be harmful to the environment and may contribute to individuals' developing cancer or allergies. Renewable resources, like sun and wind, do not have bad side effects. Through science the sun may help us fuel more environmentally friendly homes, cars, and much more.

Little Lions Experiment:

For this month's experiment, you need to talk your parents or an adult family member into taking you to the Clean Energy Expo at Penn State. This event is free and will take place from April 2-3, 2004, at the Bryce Jordan Center. Check it out on the web at http://www.wppsef.org/cee/. Once you are at the expo, visit the Penn State Science Lions booth where you can do some actual hands-on energy experiments!

If you are not able to make it to the expo, search your home for ways to cut down on use of electricity and other resources. For example, figure out ways to conserve water while showering or washing your dishes. Or, research how to start a recycling program in your home, school, or neighborhood.

Resources:

Chapter 8: Fossil Fuels- Coal, Oil and Natural Gas; found at http://www.energyquest.ca.gov/story/index.html.

A Primer on Sustainable Building. Rocky Mountain Institute, 1998.

Dr. Riley with the Penn State American Indian Housing Initiative found at www.engr.psu.edu/greenbuild.

Author:

Science Lions wrote this article with the help of Amy Grommes, a graduate student in Architectural Engineering at Penn State. Amy studies architectural sustainability and works on using straw bales and other "green" (environmental friendly) materials to build homes for the Northern Cheyenne in Lame Deer, Montana. View Dr. Riley's website for more information on this project.

What is Love?

Valentine's Day is full with heart-shaped candy, cards, and decorations. But, is the heart the only thing involved in falling in love? No. People in love often feel what they describe as a love "high." Professor Semir Zeki and his team of researchers at the University College London wanted to find out what parts of the brain are involved in this "love high." The professor and his team tested 17 young men and women who had fallen in love in the previous six to twelve months. Each of these research participants had their brain scanned. The scans help measure changes in blood flow. These measures were taken as the research participants looked at a photo of their loved one. Measures were also taken when the participant looked at three other photos. These other photos were pictures of individuals of the same gender, but were only friends. The research team noted changes in the blood flow in the brain. There was heightened activity in four areas when the individual looked at the photo of his or her loved one.

The four hot spots were the anterior cingulate, the medial insula, the putamen and the caudate nucleus. The anterior cingluate is the section of the brain that is towards the bottom of the brain. The anterior cingluate is known to be involved with responding to drugs that induce feelings of relaxation. It is associated with happy states, attention to one's own emotional state, and especially social interactions. The second region is the medial insula. This section can be viewed from the top. The medial insula is related to a host of emotional functions. The third and fourth sections are the putamen and caudate nucleus. They are in the back of the brain. The putamen and caudate lie deep in the brain. Both are frequently stimulated when we experience both positive and negative emotions.

Professor Zeki was pretty excited about these findings as he explained: "...we have discovered that this overwhelming state of love--which mobilizes your whole life--is actually controlled by four small areas of the brain." The team also found out what is not activated in the brain by their lover's photos. Some of these regions have been found to be related to sadness and can be overactive when people are depressed.

Little Lion Experiment:

Psychologists are scientists who study the mind and behavior. Psychologists study a variety of parts of the human experience from the functions of the brain to the actions of nations. They study child development to the care of the aged. One tool psychologists use to study the mind and behavior is pictures and a notebook. They use the pictures to ask their patients questions about how they feel and what they are thinking about when they look at these pictures. Cut through the newspaper and some magazines (after people are done reading them) and then ask your friends and family about the pictures. Take notes of their answers and see if certain pictures made more people happy or sad, excited or scared, or any other terms that the participants come up with. Be creative and you will find the brain is creative too.

How Do Airplanes Stay in the Air?

Flying for the holidays? Or, did grandma fly in to visit you for Christmas? Have you ever wondered--while on a plane or watching one--how a heavy, metal plane flies through the air?

Whether you are scared of flying or not, the answer to this question is a little frightening. Physicists and aeronautical engineers continue to debate the basic mechanics of flight. This is even more suprising when you consider that the Wright brothers invented the plane over 100 years ago! In spite of the debate, everyone agrees that flight boils down to physics. Yes, this means that no invisible strings are hanging from space!

Most will go on to explain that a plane's ability to fly results from air traveling faster over the more curvaceous top surface of the wing than under the flatter bottom surface. The quicker a fluid like air moves, the less pressure it exerts. This phenomenon is known as Bernoulli's principle and was discovered by Daniel Bernoulli, an 18th century Swiss mathematician. The principle helps us to understand how slower moving air below the wing exerts more pressure on the wing than the faster moving air above it. This results in an upward force called lift. Lift pushes the aircraft upward against the downward pull of gravity.

This principle is well-accepted and accurate, but it does not help us to understand why the air flowing over the wing moves faster. This lack of explanation causes confusion among physicists and aeronautical engineers. One of the leaders in helping to explain this phenomenon, Jef Raskin, actually started his research by arguing with one of his middle school teachers. He argued that this principle didn't make sense because he had seen planes fly upside down. Raskin felt that Sir Isaac Newton's laws of motion were a better explanation, as "a wing is just a device for forcing air down." According to Newton's third law, for every action there is an equal and opposite reaction, so the downward force that the wing applies to the air produces an upward force of the air on the wing. The amount of air directed downward depends on the angle of the wing (the angle of attack) and not the shape of the wing. This would help explain why a plane can fly upside down.

Although Newton's law helps to explain how planes can fly upside down, most believe that both Bernoulli and Newton help to explain flight. They also recognize that curves on the top of the plane are important and without them an airplane may stall and fall.

Flight is a fascinating science, and many aspects of why we can fly are still under debate. Start asking your teacher questions and maybe you will help get some of the debate of flight mechanics off the ground!

Source: Chang K. "What Does Keep Them Up There?" New York Times. 9 December 2003.

Little Lion Experiment

An important concept in understanding how objects move is gravity. Gravity is the tendency of matter toward some attracting body, particularly towards the center of the earth. To understand the effect of gravity or a flying objects attraction to the ground, drop varies objects such as a piece of paper, a shoe, a book, and a feather from a table. Guess, watch, time, and test which object falls the fastest.

Gravity adds weight or force - an equal amount to each object. But, gravity increases the force or speed of motion on the heavier objects. Thus, the heavier objects such as a shoe or book would beat a piece of paper or feather. You can also feel this principle at work when you slip on ice with and without your book bag! Be careful this winter!