Energy Transfer and ThermodynamicsDemonstrate an understanding of the first and second laws of thermodynamics and their applications. First Law of Thermodynamics: Energy can be changed from one form to another, but it cannot be created or destroyed. The total amount of energy and matter in the Universe remains constant, merely changing from one form to another. The First Law of Thermodynamics (Conservation) states that energy is always conserved, it cannot be created or destroyed. In essence, energy can be converted from one form into another. Click here for another page (developed by Dr.
John Pratte, Clayton State Univ. , GA) covering thermodynamics. The Second Law of Thermodynamics states that "in all energy exchanges, if no energy enters or leaves the system, the potential energy of the state will always be less than that of the initial state. " This is also commonly referred to as entropy. A watch spring-driven watch will run until the potential energy in the spring is converted, and not again until energy is reapplied to the spring to rewind it. A car that has run out of gas will not run again until you walk 10 miles to a gas station and refuel the car.
Once the potential energy locked in carbohydrates is converted into kinetic energy (energy in use or motion), the organism will get no more until energy is input again. In the process of energy transfer, some energy will dissipate as heat. Entropy is a measure of disorder: cells are NOT disordered and so have low entropy. The flow of energy maintains order and life. Entropy wins when organisms cease to take in energy and die. Appraise the elementary concepts in combustion: types of combustion, heat of combustion, combustion temperature and chemical equilibrium. The investigation of the students preconceptions brought up several hints to tie up to.
Together with the predictions of the experts the aim is to find guidelines for the work with elementary school students where their special pre-knowledge is to be considered and included into the didactic requirements given by the experts. The method of Concept Mapping will form the promoter for learning concepts more efficient and therefore morelasting. The combination of all three parts of the study as well as the guidelines for the Didactical Structuration are still in process and therefore can not be further explicated Here. In a homogeneous mixture with an equivalence ratio, of the actual fuel-air ratio to the stoichiometric fuel-air ratio) In 1.0, the flame speed is normally of the order of 40 cm/s.
However In a spark-ignition engine the maximum flame speed is obtained when (f) is between 1.1 and 1.2, i. e., when the mixture is slightly richer in stoichiometric. If the equivalence ratio is outside this range the flame speed drop* rapidly to a low value.
When the flame speed drops to a very low value, the heat loss from the combustion zone becomes equal to 11 in amount of heat-release due to combustion and the flame gets extinguished. Therefore, it is quite preferable to operate the engine within an equivalence ratio of 1.1 to 1.2 for proper combustion. However, by introducing turbulence and incorporating proper air movement, 1.1 in flame speed can be increased in mixtures outside the above range.