Science universe: Physics articles

Green Market electric utilities In 1998, restructuring of the electric power utilities opened the market place to “Green Power Markets” that offer environmental features along with power service. Green power sources will provide clean energy and improved efficiency based on technologies that rely on renewable energy sources. Educating the consumer and providing green power at competitive costs are seen as two of the biggest challenges to this new market. The Center for Resource Solutions in California pioneered the Green-e Renewable Electricity Branding Program that is a companion to green power and certifies electricity products that are environmentally preferred. Results and the future Efforts to increase public consciousness about energy efficiency issues have had some remarkable successes in the past two decades. Despite the increasing complexity of most developed societies and increased population growth in many nations, energy is being used more efficiently in almost ever...

Energy efficiency Energy efficiency refers to any process by which the amount of useful ene r g y obtained from some process is increased compared to the amount of energy put into that process. As a simple example, some automobiles can travel 40 mi (17 km) by burning a single gallon (liter) of gasoline, while others can travel only 20 mpg (8.5 km/l). The energy efficiency achieved by the first car is twice that achieved by the second car. In general, energy efficiency is measured in units such as mpg, lumens per watt, or some similar “output per input” unit. History of energy concerns Interest in energy efficiency is relatively new in the history of modern societies, although England’s eighteenth century search for coa l was prompted by the de- cline of the country’s forest resources. For most of the past century, however, energy resources seemed to be infinite, for all practical purposes. Little concern was expressed about the danger of exhausting the world’s supplies of coal,...

Physical energy budgets Physical energy budgets consider a particular, defined system, and then analyze the inputs of energy, its various transformations and storages, and the eventual outputs. This concept can be illustrated by reference to the energy budget of Earth. The major input of energy to Earth occurs as solar electromagnetic energy. At the outer limits of Earth’s atmosphere, the average rate of input of solar radiation is 2.00 calories per cm2 per minute (this flux is known as the solar constant). About half of this energy input occurs as visible radiation, and half as near-infrared. As noted previously, Earth also emits its own electromagnetic radiation, again at a rate of 2.00 cal/cm2/min, but with a spectrum that peaks in the longer-wave infrared, at about 10 æm. Because the rate of energy input equals the rate of output, there is no net storage of energy, and no substantial, longer-term change in Earth’s surface temperature. Therefore, Earth represents a zero-sum,...

Energy budgets An ene r g y budget describes the ways in which energy is transformed from one state to another within some defined system, including an analysis of inputs, outputs, and changes in the quantities stored. Ecological energy budgets focus on the use and transformations of energy in the biosphere or its components. Solar electromagnetic radiatio n is the major input of energy to Earth . This external source of energy helps to heat the planet , evaporate water , circulate the atmosphere and oceans, and sustain ecological processes. Ultimately, all of the solar energy absorbed by Earth is re-radiated back to spac e , as electromagnetic radiation of a longer wavelength than what was originally absorbed. Earth maintains a virtually perfect energetic balance be- tween inputs and outputs of electromagnetic energy. Earth’s ecosystems depend on solar radiation as an external source of diffuse energy that can be utilized by photosynthetic autotrophs, such as green plants, to ...

Magnetic energy A magnetic is a piece of metal that has the ability to attract iron, nickel, cobalt, or certain specific other kinds of metal. Every magnet contains two distinct regions, one known as the north pole and one, the south pole. As with electrical charges, unlike poles attract each other and like poles repel each other. A study of magnets allows the introduction of a new concept in energy, the concept of a field. An energy field is a region in space in which a magnetic, electrical, or some other kind of force can be experienced. For example, imagine that a piece of iron is placed at a distance of 2 in (5 cm) from a bar magnet. If the magnet is strong enough, it may pull on the iron strongly enough to cause it to move. The piece of iron is said to be within the magnetic field of the bar magnet. The concept of an energy field was, at one time, a very difficult one for scientists to understand and accept. How could one object exert a force on another object if the two w...

Energy Energy is a state function commonly defined as the capacity to do w ork . Since work is defined as the movement of an object through a distanc e , energy can also be described as the ability to move an object through a distance. As an example, imagine that a bar magnet is placed next to a pile of i ron filings (thin slivers of iron meta l ). The iron filings begin to move toward the iron bar because magnetic energy pulls on the iron filings and causes them to move. Energy can be a difficult concept to understand. Un- like matte r , energy can not be taken hold of or placed on a laboratory bench for study. We know the nature and characteristics of energy best because of the effect it has on objects around it, as in the case of the bar magnet and iron filings mentioned above. Energy is described in many forms, including mechanical, heat , electrical, magnetic, sound, chemical, and nuclear. Although these forms appear to be very different from each other, they often have mu...

  Waves and Sound In This Chapter: ✔ W aves ✔ W ave Properties ✔ Logarithms ✔ Sound ✔ Doppler Effect Waves A wave is, in general, a disturbance that moves through a medium. An exception is an electromagnetic wave , which can travel through a vacuum. Examples are light and radio waves. A wave carries energy, but there is no transport of matter. In a periodic wave , pulses of the same kind follow one another in regular succession. In a transverse wave , the particles of the medium move back and forth perpendicular to the direction of the wave. Waves that travel down a stretched string when one end is shaken are transverse (Figure 10-1). In a longitudinal wave , the particles of the medium move back and forth in the same direction as the wave. Waves that travel down a coil spring when one end is pulled out and released are longitudinal (Figure 10-2). Sound waves are also longitudinal. Figure 10-1 Figure 10-2 Wave Properties The period T of a wave is the...

Equilibrium In This Chapter: ✔ T ranslational Equilibrium ✔ Rotational Equilibrium ✔ Center of Gravity ✔ Finding a Center of Gravity Translational Equilibrium A body is in translational equilibrium when no net force acts on it. Such a body is not accelerated, and it remains either at rest or in motion at constant velocity along a straight line, whichever its initial state was. A body in translational equilibrium may have forces acting on it, but they must be such that their vector sum is zero. Thus the condition for the translational equilibrium of a body may be written ∑ F = 0 where the symbol ∑ (Greek capital letter sigma ) means “sum of ” and F  refers to the various forces that act on the body. The procedure for working out a problem that involves translational equilibrium has three steps: 1. Draw a diagram of the forces that act on the body. This is called a free-body diagram . 2. Choose a set of coordinate axes and resolve the various forces into the...