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In today’s modern, technological society the term “energy conservation” is generally described as meaning “conserving energy”, in the sense that we aim to use less “energy” to do the same amount of “work” Examples Include: •Improving insulation of houses and other buildings • Improvements in the efficiency of lighting and other electrical devices •Making cars which use fuel more efficiently However in technology and science the ‘Conservation Of Energy’ has an older and different meaning. It is looked upon as a rule. The 1st law of “Thermodynamics” is also known as the: “Conservation Of Energy” The principle of the conservation of energy states that: “energy can neither be created nor destroyed” Therefore is can only be changed from one form to another… “Transformed’ Or “Converted’ By this we mean that: “For a closed system, where no energy goes in or out, the total energy within the system must always be the same, although its form may change”. For example if we consider a pendulum: The formula to calculate the potential energy is: E(p) = m x g x h The mass of the ball = 10kg The height, h = 0.2m The acceleration due to gravity, g = 9.8 m/s^2 Substitute the values into the formula and you get: PE = 19.6J (J = Joules, unit of energy) The position of the blue ball is where the Potential Energy E(p) = 19.6J while the Kinetic Energy E(k) = 0. As the blue ball is approaching the purple ball position the E(p) is decreasing while the E(k) is increasing. At exactly halfway between the blue and purple ball position the E(p) = E(k) The position of the purple ball is where the Kinetic Energy is at its maximum while the Potential Energy E(p) = 0. At this point, theoretically, all the E(p) has transformed into E(k) Therefore now the E(k) = 19.6J while the E(p) = 0. The position of the pink ball is where the Potential Energy E(p) is once again at its maximum and the Kinetic Energy E(k) = 0. We can now say and understand that: E(p) + E(k) = E(p) = 0 - E(k) The sum of E(p) and E(k) is the total mechanical energy: Total Mechanical Energy = E(p) + E(k) NB: This is with the absence of outside forces such as friction Using our “common sense” we know that it's impossible for the pendulum to swing higher than the height (h) without giving it a push yourself (i.e. adding extra energy). If there was no friction, the pendulum would swing back and forth forever because of the law of conservation of energy. On the other hand, in an open system such as a power station, this rule leads to the conclusion that the total energy input to the system must be exactly equal to the total energy output. The extent to which the output energy is able to do useful work that is, of the desired type is called the efficiency of the system. We calculate this by comparing the useful output from the system with its energy input. How energy can be converted or transformed is of prime importance to the technologist. Some forms of energy are directly interchangeable (for example potential and kinetic) but others need to go through several changes to arrive at the final desired form (for example chemicalheatkineticelectrical. A light bulb converts electrical energy into light energy. ELECTRICAL ENERGY LIGHTBULB LIGHT ENERGY