The Nature of Energy II
Energy is a scalar quantity that can perform work in various forms. It has many forms including heat, motion, and light.
- The law of conservation of energy states that “energy can never be created or destroyed” but it can be transformed into other types of energy.
However, Einstein’s equation:
e=mc^2
is a formula where e is energy, m is mass, and c is the speed of light. Mass can be converted to energy, and this equation shows how. The energy produce will be equal to the mass of the object (usually a neutron) times the square of the speed of light.
Mechanical energy has 2 forms, kinetic and potential. These kinds of energy are what cause motion in physical objects.
- Potential energy can be defined as stored energy, and kinetic energy as the energy possessed by an object’s motion. In potential energy there are further divisions, such as gravitational potential energy, elastic potential energy, and electric potential energy.
- Thermal energy, or heat, could also be considered mechanical, although the motion it causes is mostly on the atomic level. The total amount of thermal energy, or heat, in an object is simply a measure of the movement of its atomic components. The hotter an object, the faster the atoms are moving. Thermal energy can cause motion on a larger scale as well, such as when water is heated to steam, which then rises due to its lower density. Steam can be used to turn turbines and do work.
- Waves are a way to transport energy. Mechanical waves need a medium in which to move, and electromagnetic waves do not. Sound waves, ocean waves, and shock waves are examples of mechanical waves. In mechanical waves, energy is moved through a medium, but returning the medium to its original resting position once it has left. A mechanical wave moving through a solid medium, such a rope will cause the whole rope to move at one time or another, but once the wave has passed through, the rope returns to its original position. When one end of the rope is fixed, the energy doesn’t transmit, it only reflects. The loss of energy and seizing of the wave is only caused by the air around the rope that gets moved during the motion of the wave, unless some energy is lost to the motion of the fixed end, such as a loose ring stand.
Sound waves are longitudinal, and the wave vibrates parallel to the direction of the waves motion, whereas the wave in the rope or on the ocean is transverse and vibrates perpendicular to the motion of the wave.
- Electromagnetic waves do not need a medium in which to transfer energy. This is because they are self propagating waves, which means that the electric and magnetic forces produce the other. If the electric energy propelled the wave along a vertical plane, it would produce a magnetic wave that propelled it along a horizontal plane.
- Sound waves are generated by the compression and expansion of air as the energy moves through it. Sound waves spread from a central point in a spherical motion, that is, every direction. The speed of a sound wave is determined only by the medium in which it is moving through. The more elastic the medium, the faster the sound wave can move, and also the longer distance it can travel.
- Light is an electromagnetic wave, as well as a mass less particle known as a photon. Many chemical reactions produce light as a product, like the burning of tungsten in an incandescent light bulb. Although the photon is considered mass less, it is however affected by gravitational forces.
- Visible light makes up a very small part of the entire electromagnetic spectrum, only extending from 400 to 700 nanometers. The longer wavelengths have less energy than the shorter ones, because their speeds are the same so more energy can be moved in a shorter time when the wavelengths are shorter.
- Color is simply different wavelengths of light. Red is the longest and least energetic, and violet is the shortest and most energetic wavelength of light. Pure light is white light, which contains all the wavelengths of light. A Venn diagram of color contains 3 circles, red, green, and blue. Where they meet in the middle they produce white light.
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