The Different Forms of Energy
Heat energy might be what one would think of first when asked to name a form of energy. Heat is something everyone is familiar with, whether you are in Minnesota in the winter and wishing for more heat, or in Arizona during the summer and wishing there were less. Much of the heat energy we receive is from the Sun; however, humans have been able to make other sources of heat, primarily fire. Earlier, we said that friction causes heat. The reason why is that the atoms and molecules in each object start to move faster against each other. So heat can be described as the energy of moving atoms. The higher an object’s temperature, or the measurement of heat, the faster its atoms are moving. That is why water freezes into a solid below zero degrees Celsius, and turns into steam above 100 degrees Celsius.
Besides heat, energy comes in other forms. Living in California, you must have seen surfers riding waves of water toward a beach. Water energy is found in the form of waves. Water waves can find energy from several sources. Usually, anything from strong winds to the Moon’s gravitational pull can cause waves. Sometimes, though, a wave can grow into huge wave called a tsunami that can cause extensive damage and deaths.
Where does the water obtain the extra energy to produce such large, devastating waves? Well, have you ever dropped a pebble into a bucket of water? What happens? You see circular waves emanating outward from where the pebble broke the surface. The kinetic energy from the pebble causes wave energy in the water. Often, if an earthquake occurs in or near the ocean, the colossal energy produced by an earthquake will be carried throughout water. As, the energy wave gets nearer land, the depth of the water shrinks and forces all that energy into a smaller and smaller area, thus raising the water higher than normally possible. This is a tsunami, and one struck Japan when an earthquake occurred in Chile in 1960. Taking 22 hours to reach Japan from Chile, the tsunami ended up causing the deaths of 138 people in Japan.
Sound energy is also found in the form of wave energy. Sound is produced by any object that vibrates. Music, depending on one’s tastes, is when sound from vibrations is produced in a pleasing manner. When music is played through stereo speakers, it is the movement of the speaker’s cone that compresses the air molecules next to it, causing sound waves to emanate.
The frequency of sound is the number of complete waves produced each second, measured in hertz. A wavelength is the distance between two crests or two troughs of a wave. A crest is considered the top-most point of a wave, or peak. A trough then is the lowest point, or the valley, of a wave.
The importance of frequency can be seen when discussing how humans and animals communicate. Certain animals can produce sounds that cannot be heard by us or other animals, but they can hear them just fine. For example, dolphins can produce sounds 6 times higher than what humans can hear. But humans can speak in tones lower than what dolphins can hear. Elephants can make sounds even lower than what humans can hear.
Like other waves, sound will reflect, or bounce off, a surface. The smoother the surface, the more reflection back to its source will occur, producing an echo. Higher frequency sounds will tend to reflect off a surface more than lower sounds. This is why all you hear coming from your neighbor’s loud stereo is bass. It goes right through their walls and into yours!
Scientists believe that one reason why elephants make such low frequency sounds is to communicate over long distances. Lower sounds, such as from a bass drum, do not reflect as much as higher sounds do. Therefore, elephants use low frequency sounds when communicating over long distances, because the sound waves will not reflect back and lose strength.
Sound tends to travel in a straight line, but, besides reflection, it also demonstrates two other properties that allow it to change directions. Refraction is the bending of waves around a boundary. Diffraction is the spreading out of waves behind or around a barrier. These two properties allow us to hear someone around a corner or in another room.
Architects use these properties of sound waves when designing opera houses, concert halls, and some auditoriums. They must use the proper materials and shape the hall in a way that produces the best quality sound, no matter where you are sitting. Many believe it is impossible to create a perfect hall, but in Los Angeles, there is an auditorium that is supposedly too good! Many of the musicians have complained that from where they sit, they can hear people whispering from many rows away.
Ah, electricity! What would we do without it? In 2003, people in in the northeastern United States had to find out the hard way as entire states lost their electrical power. Electrical energy occurs by the movement of electrons found in the atoms of all things. The negatively charged electrons do not always stay in their original atoms, but often travel to other neighboring atoms. When they travel, they produce energy. For example, when you walk across a carpet and then touch a metal object, electrons are transferred from the carpet to your body, and then when you touch metal you feel a shock as they all jump into the metal. This is called static electricity.
Electric current occurs when a flow of electrons is forced to leave one place for another, usually to be used as energy to do work. They travel through a material that is receptive to the movement of electrons, called a conductor. Good conductors are anything made of metal. Batteries are an example of where electrons will flow in one direction from the negative end of the battery to the object, such as a light bulb, then to the positive end of the battery. Lightning is also another form of electrical energy. Electrical energy is one of the most useful forms of energy we have, and, possibly, one day we will be able to use the electrical power of a lightning bolt to energize an entire city.
Magnetism is the phenomenon where a field is produced with the ability to either attract or repel. Magnets are objects that demonstrate these abilities. Magnets are able to do so because they have two regions, or poles, where the magnetic force is very strong. When magnets are brought together, opposite poles attract each other, while like poles repel.
Electricity and magnetism always go hand in hand. Whenever you have an electrical current flowing through a wire, a magnetic field surrounds it. By using an electric current, you can magnetize a piece of iron. You can try this experiment at home. You will need one battery, such as a D-cell battery, one compass, and some wire. Set the compass down on a flat surface and lay the wire close to the compass. Now attach the wire between the positive and negative ends of the battery. You should see the needle of the compass swing towards a different direction than previously pointed to, which should have been north. The reason this happens is that the compass needle is a magnet and is sensitive to the magnetic field produced by the electrical current flowing through the wire. For a more obvious effect try wrapping the wire around a nail and then connect to a battery. The tighter you wrap it, the greater the effect on the compass.
Magnets also attract iron, which is not a magnet but it is attracted to both poles. Magnets are all around you. You probably have some on your refrigerator right now. The Earth itself produces a huge magnetic field encircling the globe, allowing us to use compasses. Without that magnetic field, who knows how long it would have taken European explorers to find America.