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Published byDylan Fleming Modified over 9 years ago
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ENERGY AND POWER THERMODYNAMICS
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MOMENTUM MOMENTUM P = mv FORCE F = ma = mv/t IMPULSE Ft = mv = P (Momentum) MOMENTUM IS ALWAYS CONSERVED There has been the same amount of Momentum in the Universe since the Big Bang. Momentum lost in a collision Goes into heat, which is increased momentum of the individual Molecules within the heated object.
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ENERGY KINETIC ENERGY (energy at work) KE = 1 / 2 M V 2 W = F x d POTENTIAL ENERGY (available for work) ENERGY IS THE ABILITY TO DO WORK. WORK IS THE APPLICATION OF A FORCE OVER A DISTANCE: IT IS ENERGY USED UP TOTAL ENERGY=KE + PE = CONSTANT
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FORMS OF ENERGY POTENTIAL KINETIC All the rest are versions of the above HEAT (CAN BE MECHANICAL) CHEMICAL LIGHT ELECTRICAL NUCLEAR
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WORK WORK IS FORCE OVER A DISTANCE NEWTON-METRE JOULE
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POWER POWER IS A MEASURE OF HOW FAST WORK CAN BE DONE P = W/t POWER IS MEASURED IN WATTS WORK PER UNIT TIME JOULES/SECOND FORCE TIMES SPEED (FxV) NEWTON-METER PER SECOND P = W/t = Fd/t = Fv
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CONSERVATION OF ENERGY ENERGY IS MANIFEST IN MANY FORMS, BUT ALTHOUGH WE CAN CONVERT ENERGY FROM ONE FORM TO THE OTHER, IN A CLOSED SYSTEM, THE TOTAL ENERGY REMAINS A CONSTANT. ENERGY CAN NEITHER BE CREATED NOR DESTROYED
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ENERGY IF POWER IS STRENGTH, ENERGY IS ENDURANCE ENERGY is POWER X TIME E = Pt = Fdt/t = Fd = WORK UNIT OF ENERGY=WATT-SECOND =JOULE =NEWTON-METER
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HEAT TRANSFER CONDUCTION CONVECTION RADIATION EVAPORATION
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STEPHAN-BOLTZMANN LAW E(radiation) = a constant x T 4 KIRCHHOFF’S LAW: GOOD ABSORBERS ARE ALSO GOOD EMITTERS BLACK BODY = A PERFECT EMITTER
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WIEN’S LAW Lamda (max) = C/T The peak wavelength of the emitted radiation is inversely proportional to the absolute temperature
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INVERSE SQUARE LAW Intensity = I o /d 2 100 50 1 2 3456 * * * * ** 1- 100 2- 25 = 1/4 3- 11.1= 1/9 4- 6.25= 1/16 5- 4 = 1/25 6- 2.78 = 1/36 Radiation decreases by the square of the distance
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NUCLEAR ENERGY E = MC 2 FISSION: BREAKING A NUCLEUS APART FUSION: FORCING TWO NUCEII TOGETHER
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HEAT One calorie is the amount of heat to raise one gram of water, one degree Celsius. Specific Heat: Each material needs a certain amount of heat to raise its temp one degree; usually less than one calorie. One calorie is equivalent to 4.19 joules, enough energy to raise one gram of matter 428 metres higher.
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THERMAL EXPANSION Heat causes the atoms or molecules of any material to “jiggle”. When jiggling they need more room, so the volume increases with temperature (normally). Water is an exception: with the temp going down between 4 deg and 0 degrees, water will expand, and on freezing will increase volume by 9%. Ice has a density of 0.92; thus it floats. The lowest levels of a pond freeze last, if at all.
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CHANGES OF STATE EVAPORATION CONDENSATION BOILING – HEAT OF VAPORIZATION 540 CALORIES
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CHANGES OF STATE MELTING FREEZING – HEAT OF FUSION 80 CALORIES SUBLIMATION
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THERMODYNAMICS HEAT FLOWING IS THERMAL ENERGY WORK CAN PRODUCE HEAT – HEAT CAN PRODUCE WORK
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THERMODYNAMICS FIRST LAW: ENERGY IS CONSTANT E 1 -E 2 =HEAT INPUT - WORK DONE (You can’t win) SECOND LAW: HEAT FLOWS FROM HOT TO COOLER (You can’t break even) ENTROPY ALWAYS INCREASES EVERYTHING TENDS TO GET MORE DISORDERED (You can’t get out of the game!) THIRD LAW: AT ABSOLUTE ZERO, ALL MOTION CEASES
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THERMODYNAMICS FIRST LAW: TOTAL HEAT = CHANGE IN INTERNAL ENERGY + WORK OUTPUT CHANGE IN ENERGY = HEAT IN – WORK DONE
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THERMODYNAMICS SECOND LAW HEAT FLOWS FROM HOT TO COOLER EFFICIENCY IS WORK/HEAT INPUT PERFECT EFF. = (T hot –T cold ) T hot
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ENTROPY SECOND LAW: ENTROPY ALWAYS INCREASES ENTROPY IS A MEASURE OF DISORDER
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THERMODYNAMICS THIRD LAW: AT ABSOLUTE ZERO ALL ORDER AND MOTION CEASE
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